You will never ever get an unbiased comparison as it boils down to personal preference.
PS3 is NOT around the corner.. so do not wait for that.
XBOX is more powerful but, for me, has only one game worth getting.. The almighty Halo. One of the best games ever made. XBOX also is far and away ahead in the online department but to be honest if you want to play online.. get a pc and a decent connection.
PS2 is more of the casual gamers machine. It's swamped with mediocre titles like Fifa and lazy updates from PS1 games. There are some good games though but if you have a PS1 you will have played most of them before.
Why isn't the Gamecube in this by the way? It can keep pace with the XBOX, looks better than both the ps2 and XBOX, has a better control pad, better games (Wind Waker, Metroid Prime, Super Monkey Ball, Mario Sunshine, Smash Bros. Melee) and to top it all off, you can play as a full 3D Link in Soul Calibur 2.. mmmm
Oh and no im not a nintendo fanboy.. i dont even have a gamecube. =]