Favorite Gang: I'll go with Cubans considering they are the only real gang that doesn't attack you (unless you attack them, of course). Vance Crime Family is only made up of two people and I don't know who the Trailer Park Mafia is.
Favorite Gang car: Cholo Sabre. Enough said.
Hey, how about an order of you favorite to least favorite GTA? Here's mine:
Vice City Stories
Vice City
San Andreas
Liberty City Stories
GTA3
I haven't played any of the 2D games, so I can't include them.