I've been balancing GTAIV's Ballad of Gay Tony and GTA San Andreas lately.
I think that ideally, I'd love SA's fun with IV's overall package. In a description...I'd rather play SA, but I think IV is mechanically stronger in many areas.
For instance, driving. Once you've gotten a hang of driving in IV, it completely eclipses every past game in the series. What makes things even better is that every vehicle has their own specific strengths and weaknesses, and none of them control the same. I just finished a session of San Andreas, and every single car aside from muscle cars controlled similarly. Much more, there's no skill required in regards to driving. But driving in IV actually takes skill and practice. Drifting around corners at high speed takes effort, patience, and well timed presses. Drifting in SA requires little to no effort from the player to pull off successfully.
Then there's the wanted system. I used to criticize IV's wanted system, but I think I was handling it the wrong way. With a combination of Red Dead Redemption and a couple of goon posts, I think I've been able to come to respect, and even enjoy the fuck out of IV's wanted system after years of "not getting it". The problem with IV's wanted system is that Rockstar failed to give players information on ways that work to their advantage in mid chase, or fully explain all the rules to their new bounty system. In an example, in pre-release days, one of the bulletpoints in IV's previews was that you could switch cars mid chase and lose your trail for the police to follow. I'd try this out when I got the game but it didn't work. The trick is that it does so long as the stars are blinking and you're out of the gray area. This helps clear chases exponentially.
More than that, I always that cops would just randomly spawn like in the old days and not have an iota of smart AI, but due to a recent post at SA, about a guy dodging cops, I decided to experiment with the cop AI a bit. I learned quite a few things and that's that on foot chases are very practical in trying to lose heat. Duck into a few alley ways and you'll eventually lose the cops chasing you. If you hide in an alley, and notice the patrol cars, they will not know where you are and will be actively searching for the perp, driving slowly. This is your chance to duck and get the hell out of dodge.
In SA, just a few minutes ago, I had three stars, and after my IV play sessions lately, this bored the shit out of me. IV's wanted system is by no means perfect. I wish that cop avoidance were easier and more pronounced, and I wish that cops still actively searched, MGS style, for you, the culprit, but given under scrutiny, the AI holds up for some thrilling chases.
For the first time in years, I'm actually starting trouble, getting in chases on purpose, on low life, just to see if I can manage surviving and getting out of the cop radius. I'm blowing up cars with sticky bombs, running away before someone reports me, and seeing if I can get out of the area without one single cop noticing me.
All in all, the old GTA's are starting to feel oldhat, and I hope that Rockstar expands upon all of this in the new entry.