Tell me what about this is superior to say hades?
If you like the atmosphere and graphics sure.
But for me the gameplay was very dry even though it was difficult.
The level designs weren't anything amazing like most rougelike games.
Granted it's not really fair to compare Metroid to this since really they are two different genres.
They just share a sci Fi theme among other things
I'd initially keep the comparison to Metroid Dread, as that's where my commentary vs. yours stems from. However, Hades can be added to the mix with some of it, since you asked.
The moment to moment gameplay with even just the normal (non-true bosses) enemies is definitely better in Returnal that Dread and on par or better than Hades. This is due to both the variance of enemies per levels, their challenge factor and your guns/weapons and power-ups you get. I will say that Hades has even more variables in a typical rogue-like factor when it comes to it's rng scenarios tho, as far like the reward vs. detrimental effects that you can get. Obviously that part doesn't apply to Dread in it not being of that genre. But that said, the weapons at a base level, I'd say Returnal's are better overall.
The level design was actually very good, considering it's quasi procedural generated, the level design were dope as fukk. There's both more original assets artistically speaking designs than the usual far of these type of games (like Hades) and thus limitations to their variances in the level design layouts in some degrees than some other rng procedural generated levels in other games, but among the ones that are there are outstanding and at least take a while before you start seeing the "samey" layouts per each level.
Boss fights, Returnal definitely wins this overall. Granted, it has the "bigger/grander" scale of game type to really give that next level gravitas to it, but even just as far as challenge factor, it's at the very least equal with both Hades and Dread in that regard, for the most part. I think Dread might've been a lil more difficult in only that regardless of power ups in Dread, your defensive capabilities and/or over defense in general is kinda muted or nuetered. Like, energy tanks almost don't mean shyt when you getting hit and it takes 2+ full tanks of damage.
This might be a bit more subjective, but map and progress, while mostly dope in the non-hand holding sense in Dread, is ultimately handled better in Returnal, as it's not as confusing to know how/where to progress. Narrative/story-telling definitely better in Returnal that Dread. Might not outright be over Hades, considering how in-depth it continues to get through playthroughs. Hard to say tho tbh. Depends on how you like your narrative delivered, I suppose.
Returnal shares its dna quite a bit with Metroid period. It's obviously a bit of its inspiration. They have the same sort of isolated theme and vibe going. And it has the usual metroidvania tropes of requiring select power ups to access different areas.
