For me personally, If you only count games originally made for the console like Archbrix said, it goes:
1. N64
2. Wii
3. SNES
4. GameCube/NES tie
5. Wii U
Too many unknowns with the Wii U at this point in it's life. It's on the right track with Xenoblade X, StarFox, SMT x FE, Captain Toad et. al, and I like what I'm hearing so far about the new Zelda. It is also becoming my indy gaming machine. However, I have to know that its getting a Metroid Prime and a few more JRPGs. A Wii Sports sequel made for the Wii U from the ground wouldn't hurt either.