I say TLoZ:TP because it's more interesting to play if you've played OOT first, which I know you have. Plus I haven't played a bad Zelda game. Can't go wrong with Zelda. It's really good, I highly suggest it.
I only like it because of all the Nintendo Characters really. I find it a fun thing to do when bored or with a friend.
Skyward Sword is fantastic and makes allll of TP's errors shine. HOWEVER The real answer to the poll is Xenoblade
So addicting.... But, Xenoblade is better. It happens. Ya know, when you have narrative and have artistic merit just in your towns.
I'm gonna say Metroid 3, seeing as i believe you must have the rare Wii Metroid Trilogy version since you've mentioned only Wii games. Be one of the few to play it on that console, be unique, be hipster, be emo, be the ball, be a bee, and I can go on.
Dude, that's outdated. He should play the new KINGDOM HEARTS III: SUPER ULTIMATE 3RD STRIKE: HYPER TURBO FINAL MIX+++