This game needs its own thread at this point...looks like it's going to be huge. It's selling really well, even (surprisingly) in Japan, where Metroid historically hasn't done so well. I've had it since Friday...I'm not done with the game yet, but I'm through the bulk of it and have all of the powerups, so I'm at the "go find all the stuff before finding the last area" phase of the game now. While overall it doesn't QUITE top Prime/Prime 2 for me (my favorite Metroid games), it's the best 2D Metroid. It's definitely up to modern Metroidvania standards...while the environments and music aren't as pretty as the Ori games, in mechanics and size it's definitely on par with Ori and the Will of the Wisps.
As of right now this game is about a 9.5/10 for me. The only thing that brings it down (only VERY slightly) is how nerve wracking some of the Shinespark puzzles are. Yes, the E.M.M.I. zones are nerve wracking, but that's in a different way. The tension in those areas is more like a cross between Metal Gear and Survival Horror, it's almost a genre shift. Until you kill the E.M.M.I. and it changes back into a normal Metroid zone.
This game definitely tops Super Metroid in every way. Not to hate on Super Metroid...what it accomplished given the limitations of the hardware it was on was remarkable, and it's definitely one of the best games of all time. But this one beats it.
The best part...it pretty much finishes kicking Other M out of the timeline (after Samus Returns started it, by showing Ridley in his Omega armor from Prime 3, and subtly implying a different origin for the frozen Ridley in Fusion). It's specifically billed as Metroid 5. And when talking about the Metroids and X, it only references Zero Mission, Samus Returns, Super, and Fusion. (Yes, Prime isn't directly mentioned but the events of the Prime trilogy don't really tie into this story, since it was about Phazon - besides Samus Returns already confirmed the Prime trilogy is canon.)