When I referred to the DKC series, I actually meant 2 and 3, which for awhile I could sell for $20 and as high as $30 for DKC3. Now I get $10 for the first one and, if I'm lucky, $15 apiece for 2 and 3. So yeah the price on the first one hasn't changed, but 2 and 3 I can't get as much for anymore. And I've seen this with a lot of the classic series that people really want. Castlevania, Contra, etc etc. They just don't sell for as much as they did a few years.
In regards to CT, I think its price is staying where it's at b/c it's not super expensive. Earthbound used to be the same or $10 less than CT, and they are both about the same as far as rarity goes. The only thing that pushed the price up on EB was a combination of Ness appearing in Smash Bros and the dawning realization that a VC port wasn't forthcoming. CTs price didn't drop because it was never inflated to begin with. RPGs with followings tend to hold their value pretty well. I've actually noticed some games have had their prices drop after a VC release only to go back to what it was before since its price was pretty much where it should be at in regards to rarity and desirability. I watched it happen with Secret of Mana, for instance. Some games haven't bounced back fully, like Super Mario RPG, and some have been released too many times to ever recover (like Final Fantasy "II" and "III").
I'm not arguing that video game collecting or even reselling is going to be or has been devastated by digital re-releases. But I do think the casual "collector," the kind of person with more money than patience, is mostly being satisfied by those re-releases and so some of the inflation in prices has disappeared. And I think quite a bit of the price of Earthbound is made up by those casual collectors who have to have the game whether its worth that $100 bid they just made or not.