I got both a Wii and a 360. The Wii has more of those nostalgic type games (ie: Mario, Zelda, SSB, etc) while the 360 has more of the games that would've been on PC anyway (ie: FPS).
BUT, every port of those major type PC games always looks so downgraded when you compare to PC and PS3 and 360.
It simply proves that the Wii is able to keep above the rest of the market because of a) the target audience is quite large, b) they really made good use of selling it as a lifestyle sort of tool and made sure people heard about how innovative it was, and c) it (used to) cost than the rest of the competition.
I bought a 360 for Halo 3. And maybe DOA4. But after that, at the time we bought a Wii it didn't seem very interesting. They're slowly rolling out more RPG games, so I'm going to have to reserve judgement for later.
So what does it really boil down to? The type of games you like playing.
PS3 is getting massacred and has only gotten by selling their unit as a media center replacement Bluray player for the most part (when Bluray players cost more than PS3s, but even now it's still kind of a good deal). They could really use FF XIII right now... except that it's being delayed for a 360 version.