Emerald is well regarded as the best of Generation 3, which is the final of the traditional 2D games and can trade with Fire Red/Leaf Green (remakes of the classic)

So you have available all of the original Pokémon

I chose Pokemon Emerald because it is my favorite of the games that have been disassembled!

Maybe the internal battery died. I honestly recommend you look at GBC style handhelds or if you like the GBA style, Anbernic made one that looks insanely close to a GBA.

There also a craze of DS style emulators popping up. They all give you comfort knowing that your saves will be fine forever if you back them up, even if the device dies.

Try https://afterplay.io it’s cross platform, saves every 20 seconds and keeps your last 50 saves which you can recover from if anything goes wrong