Good to see Super Platformer Deluxe mentioned. I would categorize that with Super Crate Box as dang fine arcade action games.
In an earlier post, I mentioned strong publisher efforts by Adult Swim Games and Vlambeer. For Vlambeer, I meant to say Devolver - who published Luftrausers by Vlambeer, but also great 2D games like Not a Hero and BroForce.
I am really high on Luckslinger, a recent release. It has a demo, and I highly encouraged folks interested in the game to try that out.
Legend of Dungeon is another rogue-like I got on the cheap. I think it is excellent.
I mentioned quite a few games in an earlier post but I also wanted to plug offerings by Puppy Games, who created the Tower Defense game Revenge of the Titans, but also developed awesome retro action games like the Droid Assault, Titan Attacks and Ultratron. Droid Assault is like a spiritual successor to Berserk, Titans Attacks the same to Space Invaders, Ultratron to Robotron. Fun games.
As for games that I would qualify as quality "ports" on Steam (either from iOS or consoles): Death Rally, Halo: Spartan Assault and Spartan Strike, Batman: Arkham Origins Blackgate Deluxe Edition, Dyad, Dynamite Jack, Nidhogg and the recently updated Gauntlet
Honorable mentions include Diehard Dungeon, Capsized, Pid, Rochard, Vessel, Apatheon, Dustforce DX and Gunman Clive. These are all games that may not have been mentioned earlier and/or I have not had an opportunity to play too much ... but I have enjoyed what I have played.
Also wanted to plug for Castle Crashers and Battleblock Theatre. Those games' flash-esque appearance made me think of the gameplay/responsiveness issue brought up here in the thread with recent games compared to titles from yesteryear. I've been playing video games since the arcade/2600 days and while some games certainly don't deliver like the oldies, many of the ones I and many others cited do hold up to that standard very well. Volgarr is indeed a good example of a game that very much delivers on that front. I also think Castle Crashers and Battlebock do too (I probably enjoy Battleblock more than CC).
Howeve,r unless there is a demo, there is no substitute for trying out the games and determining that for yourself. Many of my favorite Steam 2D games I got very cheap in bundles, aka as low-risk purchases, so I'm not sure what to recommend on that front.
By the way, Zombie Shooter and Alien Shoot 2 are very underrated throwback action RPGs worth checking out (usually priced cheap).
This has been an awesome thread, keep up the great suggestions.