How does one know unannounced titles if they are unannounced?

SM3DW, Mario Kart 8, Smash Bros, Splatoon, Mario Maker, Zelda BotW were all strong games, but they all come out too late. You can bet that if Wii U in its first year had games like Splatoon, MK8D and Mario Maker for instance, sales would be quite difrent.

GTAV is easily strongest 3rd party game curently and it would be huge system seller on Switch (full handheld GTAV) also.

Here is answer.

You dont think the CEO of one of the largest video game retailers gets release info before consumers do?

Can't disagree - at their core, those are strong software; timing aside, are they half as interesting as they could be given Wii U's single Gamepad focus?

I'd argue that in Mario Kart 8's case, the hardware severely weakened it. The focus of the Wii U was the single player experience with the Gamepad; how many Wii U owners had additional Wiimotes sitting around?

I know I'm being anecdotal here, but Mario Kart 8 on Wii U was the only game in the franchise I didn't really play a lot of multiplayer - I got in about 20 hours of online multiplayer and maybe 3 hours of local; but I would guess most of the other Mario Karts I played exceeded 100 hours easily, maybe as much as 300+ hours in cases like SNES, N64, Wii, and DS (all of which I played a disgusting amount of). I think that's a large part as to why the Switch version has generated more excitement, it's because people are actually playing a lot of local multiplayer because they can pick up their Switch's and play it anywhere. I do a lot of multiplayer at the office, I can only imagine Universities. I'm seeing multiplayer games in excess of 6 players almost daily.

BotW definitely came out too late.

Splatoon seemed like one of the best fits for Wii U's hardware of any game ever released for it.

Would people play more multiplayer for SM3DW had it come out for the Wii or Switch? I would guess probably just based on NSMB Wii being a major local-multiplayer title, despite it being kind of a crap (multiplayer) experience compared to the Kirby games that came out later.

It doesn't really matter hardware, point is that those are system seller games, but they came out on system when Wii U was consider for fail (Wii U in first year was considered for fail), but if Wii U had Splatoon, MK8D and Mario Maker in its 1st year you can bet that sales would be stronger for Wii U hardware, same like Switch would lower sales if didnt had Zelda BotW, MK8D, Splatoon 2 and Mario Odyssey in its 1st year.

I'm not so sure about that. Do you buy consoles based on your perception of whether it is doing well on the market or not? Or do you buy them because there's a game on it you want to play, or a price drop occurred?

We have examples of hardware with mediocre sales to relatively dormant, only to pick up very suddenly with the launch of proper software or a price drop: NES, Gameboy, 3DS, PSX, Xbox 360, and PS3 are all examples of this to varying degrees. For Pokemon, even though the Gameboy was considered an antique, it did something so well with that hardware that people just had to pick it up and play it - and over 60% of the hardware sold after the system had seen its 9th year, with its 12th year being the highest amount of hardware it ever sold.

My thing is, I don't find that the Wii U is very interesting hardware to play games on.

Part of the issue with Wii U is that it did both things that Nintendo is known for (local multiplayer and portability) but both were kind of half-way there, you could play multiplayer, but only using old controllers; similarly, you could play portable, but only within 5 meters of the console.

On the other hand, Switch does both local multiplayer and portability arguably better than any Nintendo console has done to date. I think there's a good argument to be made that any software that benefits from portability, or local multiplayer, will immediately be stronger software on the Switch based on the hardware alone.
Mario Kart 8, for example: let's say both Switch and Wii U are available now, doing equally well - what console do you want to play the game on?
Switch, with its portability and the ability for up to 12 people to get involved using the same Switch control schemes?
Or the Wii U with its one gamepad, 4 player limit? where at least 3 of them have to use old controllers or some an alternate pro-controller?
For my money, the Switch version is far more exciting to me, even though it's got the disadvantage of being a port of a game I had years ago.

What are your thoughts?

Fact is that all those games came out when system was considered for fail and nobody really paid attention on Wii U except biggest Nintendo fans, thats a fact, but strong great games in early life could bring atentione to console before it failed.

Wii U didnt had mediocre sales, it start having catastrophic sales only 2 months after launch and all 3rd party left platform in 1st year, and later nothing relly couldnt save it.

You missing point, point is that Wii U would sell better than it did if it could get some of heviy hitters in its 1st year instead they come out when system was already dead (Splatoon, MK8D and Mario Maker in 1st year would definatly make difrence beacuse people would have reason to buy console), also you can bet that Switch would have worse sales if it didnt had Zelda BotW, MK8D, Splatoon 2 and Mario Odyssey in its 1st year, beacuse one of biggest reason why Switch is selling great is already solid number of great and strong 1st party games (4 huge hevy hitters in 1st 9 months of console on market).

I get confused when you say AC It could mean Animal Crossing, Assassin's Creed, Ace Combat, Armored Core, etc.

I would say so in the vast majority of cases ...

Just because you're head of the largest chain in just a single region doesn't mean that in the eyes of the publishers that your establishments will be more privileged compared to the other running chains ... (Heck, why would the likes of Nintendo share internal schedule with just the top brass at Gamestop or even divulge any specific plans to anyone else before the public knows ?) 

Only the developer or publisher know when the game will go exactly gold or not so it's not as if game retailers will know before hand that a game will be delayed compared to the rest of the customers ...

The line get's even blurrier between retailers and individual customers when publishers themselves are retailing digital copies so at that point there's hardly any difference between the two when the physical retailer is just reselling ...