that's a bit tricky. Both seem to hold their value becuase they never turn up around our NW neck of the woods.
Seems to me when it appears, GandG is asking close to $500 if its in good condition.
Double Dragon 2 (which I've never seen for sell in Oregon) I would venture to guess would warrant asking $500 for, but ultimatley would probably sell for $300 if the dude was in a rush.
Double dragon $200-250 in real nice condition. I could see scoring one for $100-150 though.
G&G is a strange game with regards to price. I think it must have came just before jamma got big or something as it seems to be accepted and like by those who collect pre jamma games as well as the jamma crowd. When they pop up on ebay or cl people go nuts and swear they are worth a lot of money. Yet I've seen one at about two thirds of the auctions I've been to and they usually sell in the $100-150 range. The one I have was bought at auction for $75.