Problem I had with GTA3 was that the connectivity wasn't all that great, in that sometimes it was hard to find your way around e.g. how to get on to a bridge linking the islands. You'd drive to the right place, but be too low down, so until you actually got to know the city properly (or learn a route A->B 'parrot fashion') you had to cruise around for a couple of minutes looking for the way up.
That's the great thing, exploring is the nr1 thing I like to do most in GTA games.
I only got to the second island on GTA3 (did quite a few missions though), in the end I got frustrated with the lack of mission choices and the fact that some felt like a real chore. Vice City was for the most part very slick, I didn't have too many occasions where I got lost etc.
True, the story was worse in III imo, but as I said, I liek freeroam, it's the main reason I like GTA, I've spend hundreds of hours pointlessly driving through the desert/countryside in SA checking out all 100+ cars ( even though they are alike), or terrorizing some county hippies or old grannies

. Or ramming into a bikers club with a truck and trailer so they all fall off and die

.
I can't understand why people like VC more than SA though, it is superior in everything, controls, gfx, gameplay ( gangs, swimming, and many many many more), missions ( although the story is a bit worse (certainly not bad though at all, great in fact still), it has more and nicer and more varied missions), vehicles ( many more of em, and I love tuning), MUCH MUCH better world ( countryside ***, awesome bridges you can drive on the cables with a bike ) and more than one city, swimmming, multiplayer ( samp and mta:sa are far better than vcmp and mta vc).
I could go on all day but I'll never really understand why someone can like vc more than sa, if someone does, then gta isn't really the game for that person imo.
For me SA is one of the best if not in the top 3 games ever created. And vice city, well, isn't. Nice soundtrack, Miami style, nice catching story about a drug deal superior characters compared to even SA I think, although many of them return in SA eg the lawyer ''Rosenberg'', nice humor ( candy suxx

,''easter egg'', rooftop jumping, etc) but not much more. Sa is the ultimate free roam game. ''You see I've been through the desert on a horse with no name, it felt good to be out of the rain'' ( K-DST) while driving your tuned R32 skyline through the desert is an unbeatable experience or mowing down people with a combine, or trucking around then getting out and murdering hald the population with a minigun, drive up mt. chilliad and on a mountain bike and ride off the ramp on the top, making saltos before plummeting to the ground, or releasing the bike in mid air and opening a parachute, etc... You've even got a small part of liberty city hidden in it.