The Atari 2600 had some sweet games. Back in college, there were five guys living in the house and we had a NES, SNES, Genesis, Gameboys, Atari 2600, a PC, and eventually a Playstation and the 2600 got just as much play time as anything else. This was back in the mid 1990's so the Playstation was the most kick ass thing at the time. Games like River Raid just never lose their appeal.
Pong is cool too. I think I still have a knock-off of it.