I'm looking for a Steam game that's pretty much the equivalent of Mario (other than Super Meat Boy or like Braid). Just a good, solid platformer that'll scratch the itch. If it's really popular like Ori I probably know it but don't hesitate to post. Thanks.
Mark of the Ninja
There was that furry Metroidvania game but I can't remember what it's called
While not too much like Mario, have you played Bionic Commando Rearmed? It's a remake of the original game, developed by Grin before they became Overkill Software.
Steamworld Dig is like a Metroidvania crossed with that MotherLoad flash game on Miniclip. I personally enjoyed it, was originally on the 3DS but now it's on tons of platforms.
Love is a minimalist platformer that's cheap as shit. I recall the developer at point stage posted a demo on /v/ and asked them what they thought of it.
You also have those games that some of the unlockable characters in Super Meat Boy came from.
Don't forget N, provided you haven't played it already.