I have no idea if this is related to the emulator but I just tried out both the US and Japanese Game Gear ROM's for Aladdin.
I get to the second stage and suddenly the jump button just stops working!
It's right after Aladdin and Jasmine leap from the first roof to the second.
I remember playing this game on my Game Gear back in the day and I know it was possible to get past this stage.
The SMS version, which is essentially the exact same game, works fine so far.
Haven't had a chance to load the previous version to see if it works there...