What were your problems with the other ones?
I think one of the biggest improvements, that has gone sort of unmentioned, is that they've fixed their horrible shooting mechanics. That was a barrier for a lot of people really enjoying the game. They got a lot better with Red Dead Redemption, and then even better in Max Payne 3. This looks like a bit of both, but closer to RDR.
I, for one, am completely excited to be a mindless fanboy-drone for another GTA game.
For me the problem with GTA4 was it was, maybe trying to hard? Driving the cars weren't as fun, and Niko left me cold.. i just didn't care at all...
Supposedly Five is different