alright i dont know the limits of hacking so these might be all "lol thats not gonna happen" ideas
1. snes nba jam te - add music during matches like the arcade
2. snes gunforce - faster bullet speed and all weaposn unlimmited ammmo to give it a more contra feel, increase speed overall
3. snes jurassic park 2 - same. all weapons unlimited ammo.
4. snes run saber - strider hack, including the cypherblade sound effect
5. snes secret of mana - remove the charge to 100% mechanic on attacks, make it more like seiken densetu3 battles
6. snes dracula x - add richter's SOTN moves, increase walk speed. maria playable
7. snes zombies ate - evil dead hack! or at least make sprites less cartoony
8. snes dragon ball z 2 - add the QOL changes of DBZ3 like the faster charging, (and well faster everything actually)
my other wishlist is mostly "add a 2 player co-op mode" to any game possible. especially ones that already feature co-op in the arcade version like magic sword, undercover cops or parodius.