Actually, a game with LESS graphics would be better, not everone can run GTA IV you know... 
For once, i'd like to see a female character 
So here's a list; 
-Femal character 
-Only able to carry like 3 weapons like in Hitman (ie. you could hide a sniper in a guitar case for example...) 
-Better sprinting (Nico just ran like an idiot really) 
-Customizeable weapons 
-Weapons could be concealed in a boot for example to avoide detection. 
-Realistic car damage, like in IV (without the lame flying out of the car [its pretty hard to do this really, since 70% of your body is below the wheel and an airbag woulden't let you flying out of your front window]) 
-Weapon skill rank up like in SA 
-Resisting a cop arrest, but like 50-50 of getting shot and getting killed instantly 
-Liberty City 
-Doing a mission with Claude from GTA III 
-Killing should be harder, it was too easy in III. 
-Ragdoll physics (IV) 
-Charater can talk to peds 
-Flying was dumb in GTA, the character "knew" how to pilot very well and was just dumb how he knew to do everything, piloting should be as hard/harder then it was in GTA III