I havent looked for these yet as I havent gotten my phone yet. But i had planned on perusing isohunt for these files.
they are typically vetted by users, so many thumbs up will signal safe and virus free files
I bought Rom Buddy from the Marketplace and it works well. A lot of games to choose from. I also just bought the Emulators for each system from the Marketplace too. I think I spent like 10 bucks total for all the NES and SNES games I want to play. Have been playing Diddy Kong 3 for SNES ALOTTTT