Far too much of an opinion based question, as is pretty any question remotely like this. People will simply say the lineup that appealed most to them (i.e. the console they play the most/ only own) was the best for them. You're never going to have everyone agree on one answer, so you might as well not even bother asking. All this crap really does anymore is start flame wars... Just play your damn console and be happy. Noone cares what we think at the individual level.

PC isn't a console.

Steam Machine

I think it's a bit weird to say that the WiiU has the best lineup. Sure it has the best exclusives so far, but that are just a handful of games. There is almost no third party support for WiiU meaning games like Far Cry 4, AC Unity, Destiny, Shadows of Mordor, Witcher 3 and Batman Arkham Knight won't even release for WiiU to name a few. So exclusive wise sure it's WiiU, but overall the PS4 lineup is better because of the third party support.

Nope, not out yet. Although it looks awesome.

Super opinion based question. IMO the Wii U has the most interesting library right now, but that's because I'm generally disinterested in the AAA environment on PS4/X1, so I have no reason to buy those consoles just yet.

The one with the best lineup is the one that sells more games, and hardware.

No need to go that far, just get  360 controller, and put steam big picture mode.. Then put xbmc for the media features and retroarch for your retro games and you have a setup that is made to control with a game pad! And is potentially much more potent than any console... Even with a lousy core i3 and a 50$ video card you beat the ps350... If you spend over 150$ or so on the video card you are at or above ps4 performance! .. With a bit more work.... 

Then you get on steam and look for the deals, get on Gog and humble bundle for even more opportunities and you can build a library of 5$ and less games in no time! (Even the big titles get to be discounted from time to time... When they don't just give them to you)

In terms of exclusives, the WiiU (obviously). In terms overall library quality, the PS4 and X1 are essentially identical. It comes down purely to preference.

Still not a console, as much as you would like to think it is. Even the alienware alpha s upgradeable. Once a box is upgradeable, and by upgradeable I don't mean bigger HDDs. I mean actually changing things like memory, CPU or GPU, PCU..etc. Then its no longer a console.

Back to OT: Something else I never quite understand about these kinda questions is; are these questions assuming that everyone has every console? Cause if take for instance I have only a PS4 or an XB1. Doesn't that mean that every game out tehre released on the platform is an "exclusive" to me? Cuase when I thik of the PS4 lineup.. I really don't see only exclusives anyway. I see all the games I can play on the PS4.