Have them all, and all three have there strengths and weaknesses.
I chose 360, and here's why.... From a European enthusiast perspective..
Wii has been a pain for me.
VERY!!! Slow european release schedule (still no super paper mario, no metroid till the end of November), dodgy import playing even with a chip which is now broken in the v.3 firmware. WiiConnect a great idea in principle, in practice over heats the wii - burns out the gpu and is pretty much useless as it only tells you to update, and not auto update so what's the point?
PS3!! Love region free gaming.. but what's the use when Sony have forbidden import/export shops like Play-asia from shipping to Europe?
Makes the process a bit stupid. Again the promised power of the PS3 is still like an untapped well, but it's' questionable whether it will ever be tapped - much like the ps2, we never got to the level promised from the early 'tech demos'.
Don't like the fact that games are also released a few months AFTER the 360 version. As an owner of both machines - I'm often not willing to wait 4 or 5 months for the ps3 version, and when it does arrive - so far there has been a distinct lack of quality over the version already out. (bar few exceptions like Oblivion)
Things could improve on this front though.
360...... troublesome hardware for many, but has been no problem for me. 2 machines, 1 from launch day and both working without issue.
Plenty of games, and so far for the most part the 'better' of the console version for many games.
So..... I chose 360.. But I still wouldn't want just 1 console I'd still buy all of them given the time again.

