Something is only worth whatever someone else is willing to pay for it.
www.ebay.com is a good place to start finding out what other people have been willing to pay for it, some of your games could be gems, or they are probably trash. search ebay for it, not current auctions, but ones that have finished in the past
As far as the classic systems go, I can't really say that a non-perfect 2600 will ever be worth anything much. They're the most common pre-8 bit system and I wouldn't expect more than $100-150 for yours.
The local consignment shop that I went to to look for NES games doesn't have ANYTHING Atari. But he had other systems all they way up to PS2 and XBOX. In fact, he had about 15 Nintendo systems and two boxes full of games.
I think a lot of people are holding on to their Atari's in hopes of their value going up. For me, if I saw one at a garage sale with no games, I'd probably pick it up for $20, but not much more. I liked Atari, but I do not see them around often. Unless you eBay, that is.