All I can say is that I haven't regretted my PS2 and its looking unlikely that I will. Although there are few exclusives, the exclusive XBox games that I find appealing seem a little slim. I won't pass any judgement on the GameCube because I've seen so little output from it.
Reasons why I really like my PS2:
DVD playback out of the box - This was my second (and travel) DVD player for the longest time, and was damn good at it too.
Solid 16:9 support from their games - Almost all of the games that I've bought for it have supported 16:9 displays, and beautifully at that.
Solid releases with a lot of replayability - GT3, SSX, Twisted Metal Black, and not GTA3 seem to be very worthy purchases in my book. Plus, the number of highly acclaimed titles like ICO and Silent Hill 2 are not bad for rental.
Good outlook for the future - Still some nice Namco releases to look forward to, and a little title called Metal Gear or something.
I don't think its fair to compare it to the other boxes, but it hasn't let me down technologically, and I think Sony has proven to have a good head on its shoulders.
If none of what I mentioned seems compelling, wander through the list of games for all three consoles at
www.ign.com and look over the movies and previews. Whichever console has the games you want, go for it. They're all powerful, and all seem to be well designed.