1. Splatoon (165:18)
2. Mario Kart 8 (93:27)
3. Super Smash Bros. for Wii U (89:26)
4. The Legend of Zelda: The Wind Waker HD (88:33)
5. Super Mario 3D World (56:08)

Not nearly as hardcore as some of the individuals here, but still a lot of time. I'm very surprised at how Splatoon shot up to the top in a matter of a few months. I imagine XCX or Genei Ibun Roku #FE will knock SM3DW out at some point.

Let's see

Games

Super Smash Bros. for Wii U: 121:07

Super Mario 3D World: 102:33

New Super Mario Bros. U: 91:34

Splatoon: 64:56

 Mario Kart 8: 54:57

Batman Arkham City Armored Edition: 52:52

Hyrule Warriors: 51:09

Donkey Kong Country Tropical Freeze: 49:23

The Legend of Zelda The Wind Waker HD: 47:08

Pikmin 3: 36:25

Apps

Internet Browser: 265:42

Miiverse: 84:28

Crunchyroll: 51:00

Nintendo eShop: 40:30

Youtube: 5:42

[Netflix] - 605:56 (note that my partner also uses this app without changing profiles.)
[Internet Browser] - 295:14 (primarily used for Youtube)
1.) Hyrule Warriors - 213:14
2.) Monster Hunter 3 Ultimate - 206:48
3.) Assassin's Creed IV: Black Flag - 91:19
[Nintendo eShop] - 76:14
4.) New Super Mario Bros. U - 64:56 (this includes the playtime of Super Luigi U)
5.) The Legend of Zelda: The Wind Waker HD - 62:15
6.) Assassin's Creed III - 57:32
7.) Call of Duty: Black Ops II - 54:37 (primarily used for zombies, I have played the campaign and the standard multiplayer mode and I did not find much enjoyment in them)
8.) Golden Sun: The Lost Age - 50:22
9.) Golden Sun - 45:53
10.) Trine 2: Director's Cut - 40:14


Xenoblade Chronicles X will definitely make it on this list when it releases.
I suspect that sometime in the future, Mario Kart 8 and Super Smash Bros. 4 will also find their way onto this list.
Other potential games to make it will be Super Mario Maker and Splatoon.

1. Super Smash Bros for Wii U (430 Hours)
2. Mario Kart 8 (250 hours)
3. New Super Mario Bros U (240 hours, I bought Wii U on launch day and this was pretty much the only thing I played for a while)
4. Legend of Zelda: Wind Waker HD (210 Hours)
5. Earthbound (120 hours)

Alos, hooray for second highest smash time on the site!

I come close, this means I gotta play more smash

Personally, I think Xenoblade will be my highest played Wii U game along with SMT x FE. Not sure which one will be first though. I'll probably re-play SMT x FE a lot.

I don't think anything will top Splatoon for me. Maybe Zelda if it just has a gigantic world and an amazing amount of content, but even then I can see my final Splatoon time being upwards of 500 hours if they keep releasing content on a regular basis.

I think out of the two, I'll probably spend more time with Xenoblade, just because it seems to have more content in general and the world is bigger, so I'll explore a lot. But I'll definitely spend a lot of time with Genei Ibun Roku #FE. If the story is as good as I'm hoping, I'll have to play it more than once.

Yeah. Splatoon might be #1 for me as well. Although, I'll probably end up playing through Xenoblade more than once. 

Zelda will definitely be up there for me. Probably only in the 60s hours though.

I'll be playing SMT x FE just because I know I'm going to love the combat a shit ton (I'd play through SMT IV again if I wasn't playing other games) even if the story is bad (I'm assuming it's not though. Atlus doesn't really let anyone down when it comes to story, even if they are sometimes generic)

Not gonna check because I'm lazy, but I know the rough estimates.

1. Splatoon (100ish hours)
2. Call of Duty: Black Ops 2 (80ish hours)
3. Super Smash Bros. for Wii U (45ish hours)
4. Wii Fit U (45ish hours)
5. Mario Kart 8 (45ish hours)

1) Mario Kart 8 - 46:09
2) The Wonderful 101 - 36:28
3) The Legend of Zelda: The Wind Waker HD - 23:57
4) Captain Toad: Treasure Tracker - 21:03
5) Fire Emblem - 19:29
6) Splatoon - 18:06
7) Pikmin 3 - 9:51
8) Super Smash Bros for Wii U - 8:14
9) Lucadian Chronicles - 4:36
10) Bayonetta - 3:30

That's in almost a year, my Wii U really deserves to be used more...