Pokemon Rebirth is an awesome Pokemon Emerald Hack which is made by Link2999 for GBA Emulators. This game is still in process of developing.
Pokemon Pure Gold is another Pokemon Gold/Silver/Crystal Remake with GBA graphics because ZodiacDaGreat uses Pokemon Ruby engine to make it. The game has been progressing.
Pokemon Palladium is an interesting Pokemon RPG Hack with beautiful GBA graphics and great features. It is so worth to try it out.
Pokemon Obsidian is a great Pokemon Hack with nice graphics and good storyline. This game is made by Justin, who owns two other Pokemon Hacks before and Pokemon Obsidian is the third game of him.
Pokemon Mythic Legends is an awesome Pokemon Hack that is using Pokemon Fire Red codebase. The author called it is “A firered hack unlike others”.