-Mario Kart 8
-Smash 4
-Splatoon
-Monster Hunter 3 Ultimate
-The Wind Waker HD
All are a different genre and you can easily sink 50+ hours in every single one.

Of course, 5 games are not nearly enough recommendations if you look at the consoles other great titles.

Go ahead with MH3U. That game, and Xenoblade will give you hundreds of hours of gameplay. Probably more than whatever Top 5 combined.

splatoon, mario kart 8, windwaker hd, hyrule warriors, bayonetta 2

1. Bayonetta 1&2 (action)
2. Mario Party 10 (party)
3. New Super Mario Bros U (platform)
4. Zelda Windwaker HD (RPG adventure)
5. Mario Kart 8 (Racing)

....a nice mix of sugar and spice makes everything nice =)

*You can ops Mario Party 10 for Smash, but most of my friends enjoy playing MP as the 4 player party game because of the variety of mini games, whereas Smash is just constant...smashing. (but that's not a bad thing, just depending on your group).

Mario Kart 8
Splatoon
The Wonderful 101
Pikmin 3
Wind Waker HD

Only the new Zelda or Stat Fox Zero can replace one of those for me.

Smash Wii U
Wonderful 101
Super Mario 3D World
Bayonetta 2
Splatoon

All these lists are so different. It's just crazy.

Legend of Zelda: Wind Waker HD
Super Mario 3D World
Mario Kart 8
Super Smash Bros for Wii U
Splatoon

Splatoon
Mario Kart 8
Donkey Kong Country: Tropical Freeze
Super Mario 3D World
The Legend of Zelda: Wind Waker HD
Yoshi's Woolly World

edit: I can't count.

Mario 3D World, Mario Kart 8, Splatoon, Smash Bros for WiiU and Rayman Legends ( best 3rd party game on the WiiU imo).