RPG: Fallout 1 and 2. It's old but if you're really after a strong plot and endless freedom, other games don't even come close. You get to eliminate an entire slavers group in order to free a guy named Vic, then travel to another town and sell him to slavers. Or instead, join that slavers group, ignore Vic or your main quest and start making a living by capturing tribals, junkies and hoes.

Adventure: Leisure Suit Larry 7

Unfortunately, both sequels of LSL7 and fallout 2 suck