If you like GT, then go check out Forza 2 coming out on Xbox in May. As for fighting games, Dead or alive 4 is hectic fun. Even if youve never played before, its easy to pick up and play, always a winner with guests.
I' would (and did) go Xbox route. Beside the fact it will last you a lot longer than a ps2, there as a lot of nice additional features:
Xbox live arcade - small fun games for cheap (Geometry wars alone is almost reason enough to get an xbox

)
Media streaming from PC
Very nice save game/account handling system
The 'achievement' system is actually quite cool I thought it was a stoopid idea at first, but its grown on me very nicely.
It can even play songs directly from your iPod!
Wireless controllers
Better graphics by far (even on standard tv)
Parental controls (should you want to use it)
The very slim possibility of Telkom maybe using it to provide IPTV via ADSL in the future. (long story will give more info if requested, but you should be able to find most of the info online anyways)