The amount of time I (as well as all other Metroid Fans) have waited for this game cannot be understated. The expectations were absurdly high and were not only met, but surpassed. (Except for one thing which I'll get to in a bit)
Samus in this game is genuinely the best smoothest and most satisfying to control character I've played, incredibly snappy and responsive which is very important for this game, as it can (and will) require fast series of motions.
The map design is excellent and the difficulty is challenging but not rage inducing. This game also wraps up the Metroid Saga in an incredibly satisfying way. Running around and collecting items and finding secrets is super fun.
The only real complaint that I have is that the soundtrack is mediocre, especially in comparison to Metroid's otherwise amazing legacy of OST's (my favorites being Phendrana Drifts from Metroid Prime and Upper Brinstar from Super Metroid). The music is not bad though, as I never thought "Is there a way to mute the OST?" and the Red Soil Brinstar Remix in this game is actually quite good, but that is the exception, not the norm which is unfortunate.
A minor thing I appreciate is the Sequence Breaking you can do in certain parts of the game (namely Kraid's boss fight) which rewards you very nicely for exploration.
This is an amazing game and a must play if you are a Metroidvania Fan.