do you like AMD or Intel?
I'd say that Intel is currently the best, but since Phenom will use AM2, you might as well stick with AMD for now
do you like ATI or NVIDIA?
ATI is definately better now, but NVIDIA has a much larger fanbase especially from casual users and it has nice prices for decent gaming cards
do you want SLI/Crossfire?
SLI/Crossfire are great for gamers, although they are power intensive graphics solutions
front side bus?
do you need a faster front side bus to accomodate the fastest proccesors?
etc. I'm too lazy to do the rest