So, Samus Returns. Overall, I think it was very good. I don't think it'll reach god-tier status in the fandom, but it's certainly worthy of its moniker. I'm going to be mentioning spoilers, so be warned.
Presentation
I know folks have criticised Nintendo for putting this out on the 3DS over the Switch, but even so, I think the game looks pretty nice on the 3DS. I've heard that its use of 3D is pretty sublime, and is highly recommended by folks. I can't confirm this myself, as I've got a 2DS, but it's worth looking into if you've got a 3DS. It's a bit of a pity that it only runs at 30 FPS, but it's very stable and very playable.
That being said, while the game looks really nice for the 3DS, I feel that the locations themselves don't feel as distinct as they could. To compare with AM2R, in that game, each locale was designed in such a way where they would imply a specific function in an overall Chozo settlement, you had the Temple (Area 1), Hydro Station (Area 2), Weapons Testing (I think it's Area 5 in SR) and so on. There's still some distinction, but they're not quite as obvious, there's some exceptions, like the Chozo Lab, but overall, I think AM2R gave the areas more of a distinct feel. AM2R also had the scan feature, which gave even greater depth and lore to each location. Another nuance I think is missing in SR compared to other versions is the lack of enemies as you approach the end of the game, it gave off a nice impression of how devastating the Metroids can be, and this nuance is lost in SR, as regular enemies are present as normal all the way to the end of the game.
Another issue I have is the overuse of elevators in an area. I can't help but suspect it's because SR decides to load whole areas rather than by room, and as such, the elevators serve as hidden loading screens. This does mean that areas feel more segmented in themselves, which kinda affects the interconnected feel that Metroid games tend to have.
Controls
Controls overall are fairly good, and having the circle pad for movement as opposed to the d-pad works alright. The big issue for me is when morphing to and from the morph ball, morphing in itself isn't too bad, as you can tap the bottom screen to morph instead of a double down movement. Though even so, I did find myself morphing out at some pretty inconvenient points. For example, during the Diggernaut fight, when he's using his vacuum attack, when I was up against a corner, I sometimes ended up unmorphing instead of spiderballing up the wall. This led to me getting sucked in and killed. The controls were also a bit of a fumble during the Diggernaut chase sequence. I appreciated the addition of being able to automatically morph into crevices, as opposed to morphing than spring balling into it, but having to fumble between morphing, switching beams and using free-aim can be a bit much when you've got an instakill wall of death approaching.
Gameplay
Gameplay wise, it's pretty much standard 2D Metroid. It's using the more snappier Zero Mission feel, I think, over the floatier Super Metroid feel. The Aeion abilities are a nice addition, in particular, I prefer the more methodical slowness of the phase shift over the fast pace of the Speed Booster. I have never been able to 100% Fusion or Zero Mission solely because of how frustratingly complicated some of the Speed Booster
puzzles could be, so having something which allows for more time and is more forgiving is alright with me.
The boss fights are probably the biggest attraction to this game, given how it's all about exterminating the Metroid species. The Metroid fights are pretty challenging, and require a lot of attention in order to beat in good time. I think the Fire Gamma Metroids are probably the most challenging, as you can't shoot any of their projectiles to regenerate health, and their attacks make it hard to stay in one place. It can be a bit fatiguing constantly fighting Metroids, though I don't feel it was all too bad. Arachnus was a fairly standard but still challenging boss, but I think the boss which gave me the most grief was probably the Diggernaut. It takes a lot of learning and patience to get its attacks down, but once you've figured it out, beating it is extremely satisfying. The Queen Metroid fight is much more challenging compared to AM2R's, though I feel AM2R gave a better sense of dread to the battle.
I liked using the Melee Counter during bosses, usually it meant having to get close to bosses, carrying a small element of risk, but timing it right and getting that opening is so very satisfying. I'm not so fond of having it needed so prominently with regular enemies, it's a diminished issue once you've progressed and gotten power-ups like the Wave Beam, but at the beginning it's pretty much a necessity. It can really break the pace when having to wait for the enemy to perform their melee attack for you to counter, and given how this is most prominent at the beginning of the game, it's a bit of a wall. A minor quibble, as I find I don't seem to have it quite so bad now, starting a new playthrough, but it's something I feel is noteworthy regardless. Regular mooks also seem to be lacking a little in variety, in later areas they just get recoloured. It'd been nicer to have new enemies to contend with, at the very least to help give areas a more unique feel, as I mentioned earlier.
Overall
While I did complain a bit up there, as I said at the beginning, I think this game is definitely a worthy Metroid title. I think the quibbles I have could very well be refined in a future title in this style, and I do hope the developers; MercurySteam, have a chance to build on what they've learned here, and make a truly wonderful title in the future. As it stands, they've got a pretty good foundation in Samus Returns, and with a potential sequel hook in the game (look at the Chozo Memories when you've got 100%), I think that opportunity will come.