If you don't see a game that interests you below, then check out this link to Console Classix.
Console Classix is a game library that has virtually every single game created for old school game consoles such as Nintendo (NES), Super Nintendo (SNES), Sega, Sega Master System (SMS), Sega Game Gear, Atari 2600, Coleco, Gameboy, Gameboy Color, and Gameboy Advance.
And best of all, you can play them ALL on your computer for Free. You need only go to their site, create an account, download their client + the .NET update from Microsoft (found here), and you're ready to go.
The only catch to this seemingly too-good-to-be-true offer is that you only have access to Nintendo (NES), Atari 2600, and Coleco games until you've upgraded to a premium package. But even this is too good to be true. There are hundreds of games to choose from on Nintendo (NES) alone. And who doesn't love Super Mario Bros?
If you don't want to mess with Console Classix right now, here are some other games that might interest you.