Microsoft gained so much steam with the 360 last generation and Nintendo's brand is as powerful, if not more, than Playstation's. I don't remember any bullish claims that the PS4 would be on top of the "720" before the PR disaster of 2013 happened. Xbox was on par until that day happened and it wasn't. If the reveal of the XBO showed the XBO as it is now, from both a marketing and product perspective, I don't understand how any right minded individual could think the XBO wouldn't be on top of the PS4. Many of the PS4's sales game from people who switched platforms because of that PR disaster, people who wouldn't have switched if if did not happen. The XBO has had a more compelling line up of AAA exclusive titles each year since launch than the PS4. That's something even Sony themselves has admitted. Would it be close, like it was last gen? Obviously, but the 360 didn't need Japan to lead most of the generation prior, and the XBO sure as hell wouldn't have needed it this gen.

As for Nintendo, I think people have been blinded by just how often they have fucked up in the last 20 years, because they don't seem to be able to even comprehend what not fucking up means. Even ignoring the fact that they won last generation handily, on both the home and handheld fronts, Nintendo has the most powerful IP in the industry. The last time they did everything right was with the SNES, and they won. Even if they did the bare minimum and simply made as standard console that only made the necessary consessions to compete, releasing 1 year early with that kind of graphically on par product, having third party support, having standardized modern features, and not having a massive and crippling software drought literally every year since its launch, it would have been just as fierce of competition to the PS4 and XBO as the SNES was to the Genesis years ago.

EDIT: This is off topic though. They didn't do everything right. No point discussing what didn't happen.

This is a numbers game. It is impossible to do everything right, because different consumers have different priorities. 

Number of things done right * people who like those things - number of things done wrong * people who don't like those things = sales performance

Obviously, the PS4 has done more things right for the most people, if we wanted to assign a "value" to it, it would clearly be the most valuable console currently.

Older consoles have higher marketshare but since they aren't actively being sold anymore, they don't have that same value. 

Not sure if your conclusion actually concludes whether this is 'fair' or not...

but the PS4 leading this generation is definitely well deserved.

Thèse are only the policy points you listed, Sony also made the best gaming console ever made... It's the fastest of its time, the OS has all the important features, since day 1... Instant play while installing or downloading, etc it's easy to develop for (which helps taking advantage of the ps4's specs to their full potential).

There really is not much more to want... However, having known in advance, they would probably have made it a bit more powerful?

To quote Clint Eastwood from Unforgiven: "Deserve has got nothing to do with it."

The ps4 has more games, this is measurable, for quality, I'm going to argue the same, moat multiplatform titles are better on it... If you talk about exclusive content, well, I think that the ps4 has more 90+ exclusive games than the xb1 (looking at metacritic as aggregators are the closest thing we have to measure the over all reception of games).

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Well, my conclusion states pretty easy for me why it is fair (like xbox having bad japanese support and WiiU having almost no third party).

Sony saved us from:

Always online DRM
1 copy = account bound (lend to friends thingy issue)

To me that alone means they deserve the win.
People are too quick to forget all things that could have been.

Was it fair for Microsoft to "win" last gen?

Business isnt about fairness i'm afraid.

Sony managed to market the PS4 better than Microsoft did the X1 and Nintendo the Wii U. That's all.

So, what be your guess if Nintendo and MS didn't screwed up?