Neither good nor bad, theyre just normal. They are just another way of how the free market works.

Short answer: they are good for the platform holder and the platform and bad for 3rd-parties and consumers.

In more detail:

Obviously they enhance the value of a platform. They are mostly the reason people bought certain consoles in the past.

Also good for the platform: exclusives really can lean into special features of the platform. That was great as the industry was still experimenting with ideas about controllers. Nowadays controls are for the most part more settled, although there still comes up stuff like motion controls, camera integration and the like. Multiplats cannot really use them or only superficial, exclusives can lean into it. One example is Another Code: Two Memories (called Trace Memory in America) heavily uses features of the DS for it's puzzles. That makes for some unique puzzles. It also means it was impossible to port it. Which is shown by the remake in Another Code Recollection: some of the puzzles had to be heavily modified or outright replaced with new ones.

Multiplats are better for consumers: they can decide for the hardware which offers the most convenience and be sure to get these titles. If they own multiple platforms, they can decide for each game which platform serves them most. For instance if you own a Switch and a Xbox Series X, you can buy games for which you want best graphics on the Xbox and games which you want to play on the go for the Switch.

Multiplats are good for 3rd-parties. For low porting costs they can access more customers. This is not only a question of money returns, this also helps to build a fan base for the game series. This may have been different in the past. As tools weren't as advanced and computing architecture more diverse, porting costs were much higher than today. Sometimes ports were entirely new games made from the ground up. In this times exclusives may have been more lucrative, especially if the platform holder gave additional benefits (moneyhat).

Now, new technology often can be better pushed with exclusives. We see that with early VR, but by now VR games often support multiple VR headsets. For instance No Man's Sky VR supports multiple big VR platforms, which helps them get more customers in this still small market.

I am not sure that innovative ideas are pushed with exclusives like signified above. The risk-averseness of the industry comes from inflated budgets, not multiplats. So we see indies with lower budgets and lower risks to experiment more freely, but they support often as much platforms as they can.

There is though an argument for library diversification. Platform holders have an interest to broaden the appeal of their platform. This first includes common genres, but later on you want to cover more niches to get more customers. This advantage goes away with multiplat, because the intention is to broaden the appeal of the platform. So exclusives might cover more niches. Tomodachi Life, Patapon or Viva Pinata come to mind as examples for niche games that broaden the appeal of the platform.

They're definitely good for business. Exclusives add value to a platform and help to differentiate it from the competition, much in the same way that exclusive programs differentiate TV networks (and now streaming services) from each other. If you wanted to watch M*A*S*H you had to tune into CBS, or if you wanted to watch The Simpsons you had to catch in on Fox, or if you wanted to watch Breaking Bad you needed AMC, and if you want to watch The Mandalorian you need Disney+ (just to throw out some examples). The "multiplatform" shows were the ones that ran in syndication and could run on any network, even more than one at the same time.

Likewise, a console brand's entire identity has historically revolved around high-profile exclusives, games that you absolutely could not play on a rival console. Nintendo has Mario, Zelda, Pokemon, Metroid, etc. Sega had Sonic, Golden Axe, Streets of Rage, etc. PlayStation has Gran Turismo, God of War, Horizon, The Last of Us, etc. And, at least until MS recently decided to go multiplatform, Xbox had Halo, Gears, Forza, etc.

And that last entry is a cautionary tale in regards to this subject. If I want to play the next Super Mario game, I'm going to have to buy it for Switch 2. It ain't gonna be on PS5 or XBS. If I want to play the upcoming Wolverine game, I'm going to have to buy it on PS5. It's not coming to Switch 2 or XBS. But if, say, Halo 7 is a next-gen launch title, I could just as easily get it on PS6 rather than the Xbox 5. By shifting towards releasing all of their games on PlayStation as well as Xbox & PC, MS has devalued Xbox by making it completely redundant. If I can play Xbox games on PlayStation but I can't play PlayStation games on Xbox, then what's the point of getting an Xbox unless I just really, really like the brand?

Having these distinct, competing brands is I think good for the business and for the customer, at least in principle. I've seen it argued that since console makers need to have exclusives to differentiate themselves from the competition, it gives them the incentive to take risks with their first-party output or by investing in development with external partners, whereas third parties don't have the same incentive. A recent Video Games Chronicle article addressed this, saying "One PlayStation executive during the PS4 era once told me that the reason it made so many cinematic single-player titles was partly because third-party publishers were struggling to financially justify them at the time, leaving gaps in its platform library." This makes sense, given how the AAA single-player space these days seems increasingly represented by first-party titles.

Also, while it may suck having to buy multiple consoles if you really, really like everyone's first-party titles, the competition keeps the console makers on their toes. If everyone was making functionally identical consoles that shared 100% of the same games, then what's the point of any one of them? It'd be similar to the 3DO, where there would be one standard manufactured by multiple companies. The competition between distinct platforms keeps the companies on their toes, and one platform failing gives the competition an opening to exploit by offering something more appealing to customers.

Nintendo and especially Sega fumbled the ball in the mid 90s, and Sony was able to take advantage of the situation and position themselves as the top console brand for two generations straight after Nintendo had won the previous two. Nintendo's struggles with the N64 & GameCube forced them to try a different strategy, resulting in the Wii, and their strategy of making unconventional hardware continued, which, after a stumble with the Wii U, ultimately resulted in the Switch. Sony dropped the ball themselves with the PS3, giving MS the opportunity to gain a massive amount of market share with the 360. At the start of last generation, Sony had learned from their mistakes and made a more affordable system that wasn't packed with complicated custom components, while MS botched the buildup to and release of the Xbox One. This caused PlayStation to regain most of its lost popularity, with the XBO selling only half what the PS4 did after the 360 and PS3 ended up in a near-tie globally, and even in the U.S., Xbox's best market, the XBO never could catch up to the PS4. This pushed MS to avoid making the same mistakes with the Xbox Series, and while MS could never dig themselves out of the hole they made with the XBO, it wasn't for lack of trying.

TL;DR: Competition is good for any industry, and with console gaming, platforms need quality exclusives to differentiate themselves from the competition and stay healthy. Exclusives aren't the only thing that matters for a platform's viability, but it's arguably the most important.

All agreed.

In the end:

Which platform is the most tight on its exclusives: Nintendo
Which platform is the most profitable: Nintendo
Which platform is the most popular: Nintendo

Without Nintendo's popular exclusive franchises, the Wii and Switch would not have done as well as they did.
Thanks to their powerful long running exclusives, Nintendo can launch 'underpowered' hardware and keep the costs of development down.

They are good. They are good because i think they are good. I think they are good because they are good.

Indeed. While pricing, marketing, and other factors are also hugely important, you're not going to get people to buy your system if it doesn't have exclusive games to entice people to buy it, and that's a big motivator to provide quality, unique experiences you can't find elsewhere. Nintendo was already on their A-game 40 years ago. While third-party games were largely exclusive in the 8-bit & 16-bit era (mostly by necessity given how incredibly different consoles were back then in terms of specifications), Nintendo was already hard at work putting out their own in-house games, first with ports of their arcade games and later perennial franchises like Super Mario, Zelda, and Metroid. Even back then, the list of bestsellers was dominated by first-party Nintendo games, even if those games represented a much smaller share of total software sales compared to now. Nintendo's games have always been the backbone of their systems, even back in the day when they shared much of the spotlight with third-party games published by the likes of Capcom, Konami, Square, and Enix.

Even on Sony's end, they've long understood the importance of exclusive games, even if they haven't been as reliant on them as Nintendo has been. Back in the 90s, they correctly assumed that discs would supplant cartridges (a CD could hold almost 11 times as much data as the biggest N64 carts for only a tenth of the cost, which made the format appealing to third parties), and many developers released games exclusively on PS1 to take advantage of the system's CD format. Sony also worked closely with many third parties, directly publishing and marketing multiple third-party titles including the output of Eidetic, Insomniac, and Naughty Dog, all three of which they would later acquire as in-house studios. They even published and marketed Final Fantasy VII, probably the most important title on the PS1, in North America & Europe.

While their major first-party offerings weren't as abundant back then, they were developing their own games out of the gate and already created or acquired a handful of studios, namely Polyphony Digital, Psygnosis, 989 Studios, and Japan Studio. They knew they couldn't rely on third-party exclusives forever, so they expanded their roster of first-party studios and for the past 10-15 years have put out some of their most well-regarded and successful games, with first-party software sales hitting new records on the PS4.

I'd argue that MS understood this as well, but just went about things the wrong way, taking too long to really expand their first-party efforts. They knew the Xbox needed a killer app if anyone wanted to buy one, and they got one from recently-acquired Bungie. Halo CE was to the Xbox as what Super Mario Bros. was to the NES. MS did help co-fund, publish, or gain exclusivity rights for multiple third-party games throughout the 00s, but they neglected their first-party portfolio for the longest time. In the latter years of Gen 7, the 360's slate of first-party games had been mostly whittled down to Halo, Forza, and Fable (they also owned Gears, but it was still being developed by Epic at the time). By time they put serious effort into expanding their first-party portfolio, the damage from the botched lead-up to and release of the Xbox One had already been done.

Maybe if they had a lot more in the way of must-have games it could have helped things, but now they've entirely given up on having Xbox exclusives, with seemingly all of their games, including their heaviest hitters like Halo, Gears, and Forza, coming to PlayStation. This has resulted in Xbox becoming entirely redundant, which, along with price hikes (that to be fair aren't entirely their fault thanks to tariff BS), has completely tanked Xbox sales. Unless you really, really like Xbox and feel you've sunk too much into the brand, there's not much reason to buy an Xbox anymore. As someone who played the hell out of Halo CE & Halo 2 on the OXbox, mained on the 360 in Gen 7, and still ended up getting more games on Xbox One than PS4, I'm seriously considering not even buying the next-gen Xbox and buying just a PS6. I'll keep my Series X since my social circle is all on there and I still play older Halo games regularly with some of them, but I'm going to be extremely hesitant to spend hundreds, perhaps upwards of a thousand dollars based on some speculation, on a console that has precisely zero exclusive games.