For GTA 4 there is a "fix" for AMD users at least. For me it ran like a dog (stutter, rubberbanding effect, to low FPS) even on a 7950@1170/1600MHz and 4,5GHz i5 2500k (all it's good with shadows disabled, but hey, the game looks to good with them maxed out!). Downloaded Radeon Pro, I've made a new profile for the game with the following settings:
*advanced tab - Changed "Flip Queue Size" to 3, but you can also play around with "Texture LOD" for sharper texture. Beware of flickering if you go overboard with values.
*tweaks tab - check "disabled Aero" and "Force Process High Priority". Also make sure that CPU Affinity is checked for all cores.