It's not a very interesting project to develop imo. I believe that people that are into this usually look for a challenge:
There is the obvious challenge, that you just can't miss, like pushing 3D on a GBA.
And then, there is the challenge of porting an entire game, and not some demo or short game, and having to adapt the entirety of the game to a different resolution. Which in the case of Super Metroid going to GBA would most certainly be quite annoying as a ton of rooms are exactly one screen high or wide. So how do you make these screens work when moving from 256x224 to 240x160 ?
256 to 240 is maybe simple enough. Lose 8 pixels on each side, which is half a 16x16 tile, and call it a day. Probably works most of the time. But 224 to 160 ? Now that's another topic, unless you want to keep 224 and have the player constantly scroll up and down, which is a poor user experience.
This is when the porting job moves from adapting the existing code to having to redesign rooms and thus alter the level-design. And maybe even the gamplay, such as the gravity and the height of the jumps for example.
And then the GBA has two less buttons than the SNES. Not that these buttons are of a super great use on Super Metroid. I mean the running button is shit and it was good to get rid of it. Still, some rooms absolutely require you to run. So you have to redesign them.
And then you have the boss rooms. Fixed width and/or height.
So in my opinion, a proper port that really embraces the resolution and button layout of an entire game such as Super Metroid would definitely be very challenging. And to be frank, as a developer myself, I am much more impressed by these kinds of accomplishment than 3D tech-demos or whatever. But that's just me.
An exemple that suddenly comes back to me is how SEGA and Digital Eclipse made a ton of efforts to adapt Phantasy Star I, II and III in the Phantasy Star Collection to adapt all the menu layout to the resolution. Modifying very old games and emulators to maximize the readability. Now this was some pretty impressive work back then.