I enjoyed all 3 in some fashion, but if I had to rank them for me it would be:
1. PS4
2. XBO
3. Wii U
The majority of my 3rd party games are bought on PS4, and I've enjoyed most of their big exclusives thus far (Killzone MP, InFamous, The Order, DriveClub, Bloodborne, Until Dawn, and need to get LBP3), even if overall IMO they've been slow from a first party perspective. The indie games have been really good, and overall there's a huge diversity on PS4 if you're willing to experience it, and 2016 will bring me the exclusive line-up I've been looking for.
XBO has had a great line-up of exclusives with a few new IP's and the best of 360. Unfortunately I'm only a fan of select Xbox exclusives (Forza, Gears, Killer Instinct), and I don't really know if I can count some of those games as exclusive since they've come to PC, and I've bought them there for the better graphics and performance (Ryse & TitanFall). The people I play with most are on XBO, which helps it's ranking here (mainly because me and my PS4 real friends, all have completely different work schedules). And 2016 they seem to be investing in New IP more than ever.
I literally just sold my Wii U, and it's not because I didn't like it. On the contrary I enjoyed it, it's just that I can't justify having a console and only playing / buying around 3 games per year for it. The Wii U was played for exclusives, and while I really enjoyed Bayonetta 2, Splatoon, Mario Maker, and Mario Kart, it just wasn't enough. And worse of all I just didn't enjoy games like Smash, Mario 3D World, Super Mario Bros U, Nintendoland, etc... as much as I did in previous installments. The Zelda delay was the final straw, on top of no sign of a 3D Metroid, Pokemon Snap (should have been there), Pokemon Battle sim / Colosseum 2, and more.