I'm going to throw a shout out to Environmental Station Alpha because I think it's an excellent game that flew under the radar of a lot of people when it launched. It makes some bold decisions with the story that some people might not enjoy but the gameplay is solid and the backtracking problem (which most metroidvanias have) is solved by having the level get harder as you progress.

It's cheap, it's not at all hardware demanding and it's very heavily inspired by Metroid. If you enjoy metroidvanias and you haven't played Environmental Station Alpha you definitely should.

And a secret shoutout to Noita. The dev of Environmental Station Alpha worked on Noita. It's been pushed into the roguelite category but I would argue it's the worlds first open world(s) roguelite metroidvania. If that sounds stupid but interesting, prepare to suffer because Noita is not at all easy and that's deliberate because the central theme of Noita is the pursuit of knowledge (the more you know about Noita the easier it gets).