For Gameboy, 1st party-wise I'd say we're already kinda getting close to tapped out on "exciting big names" and looking at mostly "interesting curiosities" tbh outside of the Wario Lands and DK94 and maybe a few others. Some of the more notable remaining "no major licensing hurdles or negotiations to deal with" games include:
- Balloon Kid (basically Balloon Fight, but as a platformer)
- Wave Race (that's right, it didn't start on the N64)
- Kirby Pinball
- X (a sort of proto-Star Fox kind of thing)
- Mole Mania (this one I think would actually be exciting. It's a Miyamoto game most people don't even know exists, let alone have ever played)
- Kid Icarus: Of Myths and Monsters
- the Donkey Kong Land games (basically handheld counterparts to the DKC trilogy)
- the other Game&Watch Gallery games
- Qix (mostly notable for being the origin of Mario Odyssey's sombrero/poncho outfit, but also Mario kinda does blackface in it so I could see this never getting rereleased)
- Pinball Revenge of the 'Gator
- Super Mario Bros. Deluxe (it's mostly just SMB1 but on GBC; there's some fun extras though that would be neat to have, like a mode where you race a Boo through a level)
There's also obviously Pokemon R/B/Y and G/S/C but I'm not getting my hopes up for those to just randomly drop (I'd settle for Pokemon Puzzle Challenge on GBC and Ruby&Sapphire Pinball on GBA tbh)