Hackvision is a retro gaming platform based on the Arduino. It's designed to be simple to assemble and use, and lets you code your own games and upload them using the Arduino IDE. It connects to your TV via a standard RCA connection (one for audio, and the other for composite video). The Hackvision comes with it's own controller built onto the PCB, however you can build your own or use a supported controller.
There are loads of games available: Space Invaders, Asteroids, Pong, Tetris, Sudoku, Parachute, Breakout, Worm, Elventure, Poofy Adventure, Whack-A-Rat and Starfield, plus you can code your own.
You can buy an unassembled kit for $33.95, or a pre-built kit for $43.95, which isn't bad for a hackable retro console.