After reading this forum without commenting anything, I decided to participate in my way, I don't know if that will help anyone.
I'll try to test a few emulators with different roms. Here's what I tested so far.
I'm using a New 3DS XL, last update with ironhax.
Catsfc
- Donkey Kong Country : first stage = 50fps
- Earthbound = 59fps
- The Legend of Zelda - A Link to the Past = 49-50fps
- Mega Man X : intro + Spark Mandrill = 59fps
- Super Ghouls 'N Ghosts (E) = 49-50fps
- Super Mario Mario World (E) = 50fps but seems to run better in blargsnes.
- Super Metroid = 50fps (can't shoot tho)
FCeumm
- Castlevania, Megaman 1 -> 6, Super Mario Bros 2 & 3, Tetris = smooth af, 59fps.
Genesis Plus GX
- (Game Gear) Power Rangers the Movie (ooh nostalgia) = 59fps
- (Master System) Alex Kidd in Miracle World = 59fps
- (Megadrive / Genesis) Aladdin (E) = 49fps
- Altered Beast = 59fps
- Castlevania - The New Generation = 49fps
- Comix Sonz (E) = 49fps
- Sonic the Hedgehog = 58-60fps
Gambatte
- Pokemon Crystal & Yellow, Super Mario Land 2, Wario Land = 59fps
gpSP
- Super Mario Advance 4 - Super Mario World = 59fps
- Pokemon FireRed (E) = 20fps
- Pokemon Glazed (hack) = 59fps (haven't tried battle yet)
- Pokemon Flora Sky = 26fps but won't start.
If you find this helpful and if you want me to test other games, I'm always glad to help.