So, I just finished Samus Returns. It took 9 hours to beat and 11 hours to get 100%.
SR was the first Metroid game that I've ever played for more than 30 minutes, and I have to say... it was awesome! When I started playing, I didn't expect it to be so fun. It might just be my favorite 3DS game. Now I think I finally understand why people like the Metroid series so much.
Though, one thing I am curious about is how the original Metroid 2 even worked on Game Boy. SR seems to require so many button inputs, and the map is filled with puzzles that require free-aiming and other shenanigans that seem impossible to do with just a D-pad and two buttons.