It really actually depends on what games you like.
From what I hear, the PS3 version of Fallout 3/Bioshock doesn't look as good as the 360 version, and a pretty shoddy online, and recent versions don't have backwards compatibility.. On the plus side, you have the 10 hour long movie (Metal gear Solid 4, if you didn't catch me back there), Little Big Planet, Resistance 2, Valkyria Chronicles, Uncharted, and Ratchet and Clank, not to mention the Playstation 1 games you can download, and a lot of other content, not to mention, Blu-Ray.
For the 360, you have a good chance of breaking the system, and a proprietary wireless adapter costs $100. On the plus side here, you have generally better ports (to be honest, I think this has more to do with the controller more than the system though) some good fighters, Gears of War, A decent port of the Orange box, Banjo Kazooie, better downloadable games (Rez HD, Castle Crashers, Braid, Banjo Kazooie, etc.) and a large list of JRPGs, some now, some later (most of which are exclusive to the 360)
And just to throw it in here
The Wii, it's small, fun for the whole family, Wii Fit is kinda fun, No More Heroes is a bloody fun mess, Mad World looks pretty good, Excite truck is fun, cheap system, but has a lot of shovelware, and on top of that, the fact that a lot of games force you to wiggle your arms around kind of gets rid of the point in playing video games in the first place.