Enter cab name here:
Congratulations, your cab is worth: whatever people are willing to spend on it.
Leapinlew nailed it... there is no way to really put prices on all but maybe the rarest of games, and even then its never set in stone. KBB gives you a good idea of what a car is worth.... there is nothing like that for games (at least that I know of). You can see some games go for $800 on ebay for a few weeks, then the same games are going for half that a few months later.... or double it at the right time of year.
You could just tell us what game you have and someone here will be able to give you at least an idea, but there's no way to really compile a list or else some games would read "Good Condition - $1 - $900" since it all depends on where your are... at what time... and who sees it. It's a lot like cars in that respect, but it seems to be a more pronounced effect with these games.