Metroid Prime 3
No More Heroes
Super Smash Bros Brawl
House of the Dead Overkill
Zelda: Twilight Princess
Pro Evolution Soccer 2009 (the best football game out there IMO specifically b/c of Wii controls)
Madden 09 (the way you can draw up plays at the line is sweet but it does need some more features added so wait for '10)
Trauma Center Second Opinion
Rune Factory Frontier
Strongebad (all of em)
Bit Trip Beat
Tiger Woods 09
thats a decent sample list of some of the best stuff on Wii.
Like SR said though, what are your preferences. IF its a basketball game well.... NBA Live is weak sauce. EA is putting BS effort into it. I agree w/Maniak on his buddy. However, if you like soccer, Pro Evo is tops for me. I've even converted faithful 360 FIFA players to it. They also have great golf games and EA and Sega are about to put out two tennis games that sound great so far in previews.
There is also some sweet stuff coming out this year. This summer The Conduit looks to be a bad ass online FPS. If ExciteBots is anywhere near the fun of Excite Truck and the online is smooth its a must have. No More Heroes 2 and Red Steel 2 sound pretty good so far. There is also a new Silent Hill and a Dead Space coming.
Well, TBH, now I'm not so disappointed in getting a Wii now. There's some awesome games coming out for it, like COD: Modern Warfare 2 and No More Heroes 2. Also, I'm definitely going to have Super Smash Bros. Brawl and COD: WaW, and Madden 09.
A question about Madden 09 for the Wii: Does it have Franchise Mode?