I don't know how this game went this long without this mod, but that doesn't really matter: Here it is, at last, Spelunky done Metroid-style. The title screen and music alone should fire you right the hell up.
Wait! What? Where do I get it? Unfortunately, the mod maker, joey4track, has not made it publicly available yet. He gave it to YouTuber BaerTaffy, who uploaded this video, and who is a talented Spelunky runner himself. Playing the mod cold, he's able to get through to Olmec though, sadly, Olmec is one of a few elements that does not have a Metroid universe counterpart.
Anubis, however, shows up as Ridley, the cave walls are Metroid's familiar purple rock (which, who knows, probably inspired this mod in the first place) and there are dozens of other analogues for you to enjoy in this 30 minute run.
The Metroid Mod—Spelunky [BaerTaffy on YouTube via Polygon]