I'm guessing you tried xp on a betamax. The only way vista is better than xp is it's looks.
And how is avg the worst? I'm pretty sure you work for norton now.
No, if the game is optimized badly.
EX: If the game can only use 1 core, even if there are other idle cores, it will bottleneck. If you have 4-2 cores it shouldn't be a problem.