i love all the gta games tbf, right up from the old 2d ones, but for me san an was the best, i think it has a lot to do with the fact the soundtrack has loads of the music i listened to while growing up, well that and a lil part of me that wanted to be a "menace to society" or one of the "boys in the hood" lol, ahh the good ol days.
im currently about 89% complete, ive done the oysters and horseshoes, half the tags and about 7 of the unique jumps, oh theres a few races left i think but the story missions are well over.
as you said though, sometimes i just wanna break out my harrier jump jet and go buck wild