PS2 for sure! Extremely large userbase means better support which in turn means better games. Some of the games for the system are incredible and the graphical clarity it loses to the X-Box is miniscule. The control pad is the most ergonomic and comfortable one on the market.
Online gaming for the system is also coming into full swing. Any of the new sports games is online compatible and many of the other genres have mulitplayer online capability as well.
The only quam I have with Sony is that their system crapped out on me after I had it about 2 1/2 years. I bought it on launch day, played the heck out of it, and then it died. Planned obsolescence I guess

. Any newer model should work fine however. Anyway, got another one and have been enjoying the games ever since!