I've been trying to get back Megaman Starforce Black Ace, just because I really liked that game and I wanted to play it again, and everywhere I check it's at least $30. In fact, amazon has a ton of people selling it for more than $150 (which is outrageous) I never should have gotten rid of that game in the first place. I'm going to start keeping all of my games, even if I don't play them, just because at some point I'll probably want to play them again like this and end up having no cheap way to get it
Sux man. I literally never get rid of my games. I'm a hoarder. Even if I don't play it, it's there. I think I own one game which is considered "rare" - Thousand Arms for PS. I've seen it go for a few hunnit $$$ on eBay so I might sell it at some point.
This game had a single print run, for starters. I don't know why you sold it. Could probably find a copy cheaper on eBay. The price have spiked from people trying to get it before May, 20th too and you're just experiencing the results. That and Mega Man games have spiked in value ever since Capcom stopped loving Mega Man annnnd he was revealed for Smash- people like to get to know these characters (Marth). Short version of what I'm saying, it could just be bad timing.
I know the feeling, and have very much resisted ever selling a game again for quite a few years, except for newer titles that I know won't grow in value or that I just didn't care for at all, or if I plan to get the re-released version later on anyway (like Dead or Alive 5 Ultimate.)
I'd feel sympathy for them if they didn't turn around and sell the game they just bought at $9, for +$27.
In terms of valuable games, I own a close to mint condition copy of The Legend of Zelda for the NES (in the box). It's pretty sweet. Other than that I'm pretty much just Jack Sparrow when it comes to video games.