If you're looking for some oldschool games, I can recommend La-Mulana. You can download the original version (it will need to be translated from Japanese, the translation patch is on the same website) for the PC, but they're remaking it for release on Wiiware, although that version hasn't been finished yet. La-Mulana is a really hard old school puzzle platformer, and is currently kicking my butt seven ways to Sunday. I've had a blast so far, though.
Also in the platformer style is , which actually was the game that reminded me of this style of game. It is a platformer styled after roguelikes, and as such is stupid hard, with no savepoints. At all. It's just you, your whip, and everything these magical ruins have to throw at you.
I'm a big fan of roguelikes, and am currently knee deep in the dead in DoomRL, a "coffee break" roguelike. Originally designed to be completable in about 30 mins, Kornel has made it into much more than that. Rip and tear!. It's basically doom, but instead of being a pioneering first person shooter, it's a tactical turn based bloodbath.
Another really great roguelike is Dungeon Crawl: Stone Soup. Originally created by Linley Henzell in 1995, he has since abandoned the project (to be a lawyer or something, I don't know) but a spirited group of volunteers has created the Stone Soup variant, which is very much alive. DC:SS is a roguelike game of exploration and treasure hunting in dungeons filled with deadly monsters bent on your destruction. Your goal? The mystical Orb of Zot. Get it, and get out. Simple, right? The game is massively deep, and has great replayability. Also the community is amazing. (If you find the wiki, don't trust it. It's wrong. Always.)