Does anyone know of any good modded Pokémon ROMs? -Edit- Sorry I forgot to mention that I meant for GBA
I know of some good DS hacks, not so sure about GBA. As for DS hacks: Blaze Black/Volt White Blaze Black/Volt White 2 Bloody Platinum DarkDiamond Black/White Deluxe Hack Gold DS GBA hacks: Pokémon Light Platinum (I don't really like it but you might) Pokémon Galaxy Elements (still indev, no download link, might be dead) EDIT: Yeah, Galaxy Elements is dead.
FireRed Omega is fantastic. Pokémon Snakewood is a hack of Ruby with a zombie-themed story and gameplay. Pokémon Fuligin is a new adventure, you can catch every Pokémon as far as I'm aware. There is some mature dialouge, though. All for GBA. Hope it helps!