Sega has a collection of 55 Sega Genesis ROMs for sale on Steam
Link
This has been out for a while, but I really like this bundle of games. Very fun to play on a Raspberry Pi, since they have a folder in the game's files with the raw ROMs of the games included. Also comes with a built-in emulator and manuals of the games. Pretty good amount of content for 17 USD. It is currently in the Steam sale, but I've seen it in the other Steam sales for the same price.