I don't doubt that one bit if you are talking about modern games... (if they're optimized to run on dual core)
for older games though:... what about quake 4, doom 3, half life 2 - they run on ultra settings on my PC. in 1024x768.
if i had the money, i would be running quad core, 8gb ram, crossfire.. but i don't so i have had to find a balancing point of what i'm happy with running stuff at.. and when i do come to upgrade then i will notice the jump in speed more than say someone who's gone from an 8800 to a 9800gtx..
I have had the biggest 'bang per buck' out of this machine, and in HEXUS reviews thats all that matters..