PS2: not sure, but I'd guess 60-90 at the most. (could be much less)
Games: depends on the title. If they are sports franchises probably less than a buck a game. (Sports games like madden lose significant value when the next year comes out). The rest will probably be anywhere from 1 to 10 at the most. 10 being a very good game such as cod 3.
Controller: 10-15
memory card: couple bucks
if u need money DON'T go to game stop they only give u like 5c per game and like only a couple bucks for the ps2 and memory card. ur best bet is to sell it to friends or at a yard sale.