This app was mentioned in 3 comments, with an average of 1.33 upvotes
No prob. RetroArch is definitely the best, but it is a bit tricky to use. If it's out of your level of patience or effort, I used to use NESOID for NES games, but it's got some weird control glitches.
And for GB/GBC I used to use A.D - Gamebody Color Emulator
I use this Gameboy Color Emulator, Playstation One Emulator, N64 Emulator, Sega Genesis Emulator.
Sorry took so long. Was at work when posted, got home and just passed out lol.