I have all 3 systems and I'd highly recommend the 360. The Wii was fun at first until the novelty wore off, now nobody plays it, not even the kids.
As far as the PS3 goes, it's a solid system, I never had any problems with it at all. It is a great system, however the online play kinda sucks compared to the 360 and of course, it doesn't have enough exclusives to make it worth buying over the 360. It is nice having the blu-ray player and in time, it's gonna have a couple of must have games like the new God Of War, but that's a ways off.
Now onto the 360, it's the best of the 3, I have 4 of them in my house
Online play is great, there's a good selection of exclusive games such as Fable 2. Like others say, they aren't made the greatest. I had to ship out units 3 times now and there was the 4th that shit out, but it was out of it's warranty period, so I just went out and bought another one.