If you like metroidvanias of course you should play Metroid and Castlevania. The first two metroid games are pretty rough so I'd recommend start with Super Metroid of Snes, then move on to the game boy advance games (Zero Mission and Fusion) and maybe the prime games if you can emulate or own a gamecube.
As for Castlevania you can start with Symphony of the Night, then move to Aria of Sorrow, Circle of the Moon, Order of Ecclesia, Portrait of Ruin and Dawn of Sorrow.
If you liked Hollow Knight maybe try out Dark Souls, it's not a 2d platformer but I've heard it has a pretty similar feel and it definitely gives you a sense of exploration.>As a kid I played a lot of mario
Well I'm pretty sure there's some mario games you haven't played because they release games every single year.>I tried getting into touhou, but I couldn't no matter how hard I tried
I know how you feel.