I sorta agree, yes it'll run.
Case in point: Q9550 @3.2Ghz, Radeon 5870, 8G mem would chug is several games (last few Assassin's Creed games,
Dishonoured, Max Payne 3, etc). No slouch to be honest, so there I agree.
However, getting a 3770K @4.7Ghz, Nvidia 660 and 16G of mem = SMOOOOTH gameplay in the above games.
The only time I've seen slow downs is when folding on 6 out of 8 cores with GPU folding paused...even that is rare.
The video card is not the only limiter as I found out after a bunch of research for a paper I did a while back, yes the
new cards kick much ass, but w/o modern CPUs and memory to back it up most of the benefits will not be realized.
(However, for the record you are correct, and would be spot on if most games were half-way decently threaded).