I'd very much like it if companies (big and small) would churn out 2D or 2.5D side-scrolling, metroidvania-style games....
well if you are looking for more...
Have you tried
Iji
free 2D metroidvania style with a female protagonist. Different endings based on what you choose to do. The choices isn't obvious either. Which makes it a bit interesting.
http://www.remar.se/daniel/iji.php
Iji is an action-packed strategic platform shooter with a detailed story, large levels with multiple paths, powerful bosses and lots of secrets. There are alternate gameplay events, dialogues and scenes depending on what you do, a wealth of extras and bonus features, and seven stats to upgrade through a leveling system. Iji herself has superhuman strength and abilities, and can crack Nanotechnology, use her enemies' most devastating weapons against them, and be a pacifist or a killer - the story adapts to how you play.
Mercenary Kings
Weapon crafting + metal slug style gameplay + coop.
Unfortunately it's really grindy and the mission time limits + the ability of some bosses to warp from one part of the level to another can get frustrating. I was watching while they were making this game. Paid some money too. Time limits were added because people would instead of progressing would spend eternity in one level grinding for crafting materials.
http://store.steampowered.com/app/218820/Mercenary_Kings/
From the company Alientrap: Capized and Cryptark.
http://store.steampowered.com/app/344740/CRYPTARK/
http://store.steampowered.com/app/95300/Capsized/
Cryptark is a rogue like R-Type shooter. Both is 2D graphics. Cryptark ends when you either beat the game or have enough debts that the game ends early on ya.
Since you mentioned Blade Kitten, you might like A.R.E.S.
http://store.steampowered.com/app/315340/ARES_Extinction_Agenda_EX/
It has similiar play. Ares is like an easier version of Megaman.
Now if you would like to play an harder version of Megaman that is far superior that that POS that the creator of Megaman created.
http://store.steampowered.com/app/388800/Azure_Striker_Gunvolt/
Aquaria is a 2D side scroller of a female protagonist that follows a mermaid. Very metrodvania and the map is very large and convoluted.
http://store.steampowered.com/app/24420/Aquaria/
Guns Gore Cannoli is a 2D side scroller platform that is basically about a mob hitman fromt he 1930's out to take out one guy that unleashed a zombie apocalpyse. Short though.
http://store.steampowered.com/app/322210/Guns_Gore__Cannoli/
Outland.
Every wanted to see what a fast paced 2D side scroller platformer combined with a bullet hell would look like?
http://store.steampowered.com/app/305050/Outland/
Nefarious is a 2D platformer which has you playing as the villain running away from the heroes after kidnapping princesses and wiping the floor with them. It's weird.
http://store.steampowered.com/app/448290/Nefarious/
Mark of the Ninja is a stealth based 2D platformer that is fairly well done in that you can actually skip past most the enemies without harming them if you choose to.
http://store.steampowered.com/app/214560/Mark_of_the_Ninja/
Gina Sisters: Twisted Dreams is a hard puzzle platformer with boss fights.... It reminds me of Ninetndo's Mario games which makes sense since this is a remake of one of the old Mario clone games from the 80's.
http://store.steampowered.com/app/223220/Giana_Sisters_Twisted_Dreams/
Fez is beautifully well made and extremely large and convoluted 2D platformer.
http://store.steampowered.com/app/224760/FEZ/
The Death Spank series is a 2.5D platformer that is a action platformer that revels in comedy. It's RPG like in much the same way WoW is considered an RPG. There is 3 games in this series. The problem is that each sequel is just as repetitive and similar to the first game. The games feels like somebody decided they wanted to mix Torchlight with Monty Python.
Axion Verge.
Metroidvania 2D platformer that uses "glitches" as gameplay. It can get frustrating. But very atmospheric.
http://store.steampowered.com/app/332200/Axiom_Verge/
Valid Story I wrote about above this post. It's an action 2D platformer.