I just gotta say I think GTA IV gets a lot of hate that it doesn't deserve. Until GTA V, IV has the best open world, bar none. You may not like the driving or the shooting mechanics or anything misc. thing but Liberty City in GTA IV is the most immersive and "REAL" world I have stepped into. I expect GTA V to take the crown and it should obviously.
Here's my 2 cents on the driving. I think the Driving followed the same rules of the same physics engine as the rest of the items in GTA IV. In short, I think their was a unified physics engine for EVERYTHING, which isn't good. So every item followed the same rules of physics no matter what it was. It makes sense in the real world I guess, I'm not a physics major, but it would explain why the running and the driving were bad. Everything was based on weight. I don't think Rockstar made the same mistake again twice though I think the cars now have their own physics engine as they always should and the rest of the features do as well.
From a real world driving perspective, the driving in IV was HORRENDOUS. From a gameplay perspective, it was actually easy to adjust, practice and get good at. That's why I never understood why the uproar was so huge. I get it must be hard to adjust after driving in the world but it's just like any other game; you learn the rules, practice and get at it.