I'm totally the first option. I play one game until I'm bored or done with it.
Well...I'm almost totally the first option. There is one exception. I tend to get burnt out while playing most sandbox games and need to take a good break from them. I won't quit them and never return, but I will put them off indefinitely until I feel ready to start back. This is especially true for ones set in a (at least kind of) modern city (GTA, Saints Row, Mafia, Godfather, The Saboteur). It's not so true for games like Red Dead Redemption and Assassin's Creed: Brotherhood.