I recommend mario kart. Most fun i've had with the wii so far.

It sounds like you've already made up your mind, but if you haven't yet I'd drop Zelda for Mario Kart. Zelda really did feel like more of the same, while Kart felt new. Just my two cents, though.

Metroid Prime 3
Super Mario galaxy
Legend of Zelda.

Galaxy is jaw-dropping amazing, you have to get it.

All are must buys, and when you get some extra cash..

RE 4 Wii edition
Okami
Fire Emblem

Wii Sp.... oh wait lol. That's the game I've spent the most time with on Wii anyway. Nothing beats the pain in your wrists because you've found out how to play the mini-games and get good scores doing it.

Anyway, I'll recommend a couple of games from what I've played.

-Mario Strikers can be fun, though VERY frustrating since the AI likes to go into 'kick your ass' mode and completely decimate you. Teaming up with somebody helps since you can plan your attacks and set each other up for goals.
-As others have said, Super Smash Brothers Brawl.
-Okami on the PS2 was a sweet game, that experience seems unchanged (except for painting with the Wii-mote) so I'd highly recommend this great game.
-Resident Evil 4 was kind of a meh experience for me on the PS2, perhaps the Wii and it's smooth gameplay and actual crosshair (vs the tiny laser dot on the cube/PS2) will make the gameplay better.

Zack & Wiki
Final Fantasy Fables: Chocobo's Dungeon
Sonic & The Sercet Rings
Wii Play
Dragon Quest Swords: The Masked Queen and Tower Of Mirrors

I would recommend a game called "selling Wii on eBay". Seriously, you can buy a new Wii and gain money.

id reccomend besides SSBB since your sure about getting it
SMG
MP3
LoZ:TP
MKWii

sc94597 already give you a list of great games for Wii ( ^w^)b

Super Smash Bros. Brawl
The Legend Of Zelda: Twilight Princess
Super Mario Galaxy
Metroid Prime 3: Corruption

and
BATTALION WARS II