Correct me if I'm wrong but this is a list of 43 titles published by Nintendo on GB/C, maybe I'm missing a few lol (like Wars titles):
- Super Mario Land
- Super Mario Land 2
- Wario Land
- Wario Land 2
- Wario Land 3
- Zelda Link Awakening
- Zelda Oracle of Seasons/Ages
- Metroid II
- Kid Icarus 2
- X
- Tetris
- Wave Race
- Dr.Mario (with NES this is a little redundant?)
- Pokemon Red/Blue
- Pokémon Yellow
- Pokemon Gold/Silver
- Pokémon Crystal
- Pokémon Pinball
- Donkey Kong 94
- DK Land 1
- DK Land 2
- DK Land 3
- Mario Tennis
- Mario Golf
- Kirby Dream Land
- Kirby Dream Land 2
- Kirby Pinball Land
- Kirby Block’s Ball
- Mario Picross
- Kirby Star Stacker
- Game Watch Gallery
- Game Watch Gallery 2
- Game Watch Gallery 3
- Pokémon Puzzle Challange
- Mole Mania
- Ballon Kid
- Qix
- Solar Strike
- Tetris Attack
- Tetris 2
- Super Mario Bros DX
- Donkey Kong Country (SNES downport, redundant?)
- Kirby Tilt N Rumble
Third party is hard to guess would be happy if we get Megaman 1-5 and Extreme 1/2, some Rare titles, Harvest Moon, etc
And this is Nintendo published titles on GBA, there are 54 titles:
- Super Mario Advance 1 (SNES port, redundant?)
- Super Mario Advance 2 (SNES port, redundant?)
- Super Mario Advance 3 (SNES port, redundant?)
- Super Mario Advance 4 (SNES port, redundant?)
- F-Zero Maximum Velocity
- F-Zero GP Legend
- Napoleon (japan-only)
- Kururin
- Kururin Paradise (japan-only)
- Mario Kart Super Circuit
- Golden Sun
- Wario Land 4
- Advance Wars
- Advance Wars 2
- Magical Vacation (japan-only)
- Tomato Adventure (japan-only)
- Golden Sun 2
- Zelda A Link to the Past+4 Swords (SNES port, redundant?)
- Zelda Minish Cup
- Fire Emblem: Sealed Sword (japan-only)
- Fire Emblem Blazing Sword
- Fire Emblem Sacred Stones
- Metroid Fusion
- Metroid Zero Mission
- Custom Robo GX (japan-only)
- The Legends of Starfy (japan-only)
- The Legends of Starfy 2 (japan-only)
- The Legends of Starfy 3 (japan-only)
- Wario Ware
- Mario & Luigi Superstar Saga
- Kirby Nightmare in Dream Land
- Kirby Amazing Mirror
- Mario vs DK
- DK Country 1 (SNES port, redundant?)
- DK Country 2 (SNES port, redundant?)
- DK Country 3 (SNES port, redundant?)
- Mario Gold Advance
- Mario Tennis Advance
- Mario Party Advance
- Mario Pinball
- Wario Ware Twisted
- Yoshi Tupsy Turvy
- DK King of Swing
- Mother 3 (japan-only)
- Bit Generations (japan-only)
- Rhythm Heaven (japan-only)
- Pokémon Ruby/Sapphire
- Pokémon Emerald
- Pokémon Fire Red/Leaf Green
- Pokémon Ruby/Sapphire Pinball
- Polarium Advance
- Game & Watch Gallery 4
- F-Zero Climax (japan-only)
The list goes to 41 if we exclude japan only titles, then to 33 if they are not planning to add SNES ports. (I think Mario Advance will add them)
For third parties is difficult to guess, GBA recieve good support from third parties so maybe we can get titles that got on WiiU VC like Megaman & Bass, Onimusha Tactics, Sonic Advance 1/2/3, Rayman Advance/3, Konami Crazy Racers, Klonoa 1/2, Drill Dozer 1/2, etc, or maybe nothing lol.