Mine is Lady Sia for GBA. It's just a platformer but I just love it played and completed more 20 times. Will probably speedrun it in future.
The music in that game is an absolute banger:
https://m.youtube.com/watch?v=CnP0Po665vU&pp=ygUYYWN0cmFpc2VyIGZpbGxtb3JlIHBpYW5v
Big Castlevania vibes