A third recommendation for Vanquish. You should also play Metal Gear Rising: Revengeance. Both of these are by Platinum Games, the same people who made the Bayonetta series - these people know action!
Portal 2, especially since you seemed to enjoy the first one. It's probably twice as long and it does considerably more than the first game mechanic-wise. Same great writing, too (although it's a bit more self-consciously wacky, which hurts a little bit).
Klonoa: Door to Phantomile for the PS1. Fun, kid-friendly platforming game that uses a simple mechanic (bouncing on top of a captured enemy for a double-jump) to great effect. Reminds me a bit of a Treasure or Rare game from the N64 era. There's also a graphically-enhanced remake for the Wii simply titled Klonoa, although I haven't played it and have no idea how much or little it differs from the original.
Gremlins 2: The New Batch for the NES. Not exactly a lost classic, but a surprising solid and challenging action-platformer for a licensed game. Has an overhead view similar to Crystalis and the graphics (especially for Gizmo and the Gremlins) are quite detailed for the time.
Bucky O'Hare is another well-made action platformer for the NES from a licensed property, this time a side-scroller by Konami. You can eventually switch between four different characters and the game takes a style similar to Mega Man into quirky, Battletoads-style directions without the punishing difficulty.
I'd be curious to see what you would make of the Hitman series; Hitman: Blood Money would be a good place to start. Don't know if you'd love or hate the open-ended nature of the levels and missions.
I know I've already bugged you regarding Skullgirls, but a new edition of it (Skullgirls: Second Encore) is coming to the PS4 in the next month or so. It's going to have all the DLC characters included along with some new features (including the ability to play against online against people still playing the PS3 version, which you have to admit is pretty cool). Definitely the version to get, and you get to fill out your reviews for the new systems a bit more.