So, not long ago, I came across this Metroid fan-game, and my god it's spectacular! A remake of Metroid II: Return of Samus with tons of inspiration and some assets from Zero Mission, Fusion, and Super Metroid, but still mostly with redrawn, vastly improved versions of level and enemy sprites that appeared in the original Gameboy game. The music is phenomenal, the pacing and updated level design are great, and the physics engine (read: jumping) is absolutely perfect, exactly how the gameplay of a 2D Metroid should feel, in my opinion. It's still in beta, but the demo currently available has quite a bit of content, and the gameplay itself is finished, only the later levels are missing.
For any fans of the 2D Metroids, I highly recommend checking this out. It honestly feels like an officially licensed game, maybe even better. It's totally free, and will be still when it's finished. Even if you don't fall in love with it as much as I have, it should be more than enough to tide you over until we get another official 2D Metroid from Nintendo (this year, maybe?).