some simulation games(now realistic is LOMAC btw?) and rts games do a huge and unproportional amount of cpu work compared to most games. cod2, not sure what went wrong there, when it came out the top cards were cpu limited because i dunno, its assumed just poor coding. generally 90% of games are gpu limited and you won't see large increases, sup com, COH and a bunch of rts's do see large increases in fps but then again the jump from 25-45fps in sup com isn't at all noticable, the main difference with sup com is the minimum framerate and that is noticable but its also the biggest scale rts there is. generally people only get issues at huge numbers of units and in a massive battle. even most rts's don't have issues because they aren't on that scale.
most fps's, rpg's and what not don't get huge gains at all, tiny gains but they will generally have gains. the reason i would still say go dual core is because with dual cores, quad cores and more on the horizon games makers can start to implement far more complex and time consuming physics, meaning more realistic games, better action, more cpu power for more advanced AI. most games are now writen to use dual core but still its just the ability to use both, we're not at the stage where you need both cores to deal with the physics, but games in the next year or two will do just that, NEED both cores. the physics in the next star wars game, the europhia engine, look sweet and will most likely need a very beefy cpu to run nicely.
basically, get a dual core, even a dual core ath x2, you won't see big gains now unless you basically only play a very small and specific set of games. but you'll be stabbing yourself in the foot by getting another single core.
maybe crysis will be out in a couple months and need a dual core, who knows right now. there are a lotta big games coming this year.
