If you're a serious gamer, playstation 3 no contest. wii's are fun for groups of people but unless you already have a PS3 and are looking to add to your collection or you have people over constantly, you won't use the wii as much as you think and the graphics are not comparable at all
Playstation : cons: expensive, not too many games which can use the power pros: fun, great graphics, using it to finding cure for diseases, has backward compatibility for huge selection of Playstation 2 games, upto 7 people can play locally........... Nintendo Wii: cons: some game might get boring fast, mediocre graphics, expensive nunchucks/remote,hard to find pros: fun, cheaper than Playstation 3, up to 4 people can play locally, backward compatibility for other Nintendo games......
You get a Wii if you like doing exercise. You get a PS3 if you like sitting on the couch playing Black Ops.
It depends no what you want out of a machine. A PS3 like a see someone write is your 'gamers' choice because it does have the far better game titles, where the Wii is a party/social games machine.
I've got all 3, wii, PS3, and Xbox360 and like them all for different things. Wii is mostly for using Wii Fit though some of the games are fun too. PS3 is primarily my media server, as it's so much better for that than the Xbox. ANd of course the Xbox is for those titles I can only get on Xbox, also for some of the XBL content. I won't pay for a gold account though... not worth it in my eyes. I'll play multiplayer games for free on PS3 instead.
Oh I meant to add, for kids the Wii is likely better until they hit around 13 or so... at that point the wii may seem a little too "childish".
there's a lot of game's variation in PS3, like RPG, FPS, action and action RPG, simulation and many more. so if you are a gamer's addict, then you should choose PS3. In my opinion, WII have a fun and refreshing game with colorful graphic, so it more suitable to be a tension-release console which is played in a short time period