I've never played the original Metroid 2, but I did play AM2R. That game felt mostly nice but did have a lot of really annoying archaic parts to it (boss' weak point is slightly higher than the straight line you can aim in haha get 0wned), but Samus Returns did a significantly better job of modernizing and cleaning up all the jagged edges of the game. Features like stick aiming, parrying, autosaves before bosses, and the scanner pulse made it a pretty straightforward but enjoyable metroidvania.