luciferous

Lots of great answers here, and I agree with much of what's been said, but one company that hasn't been mentioned yet is Infocom. Those games were a different animal, of course, but the fact that brand new players would have the exact same experience today that they did decades ago (without the baggage or expectations of modern graphics) is amazing.

This is an easier question than the "best games of all time" thread! Some favorites off the top of my head: Stunt Car Racer (Amiga) - Multiplayer via a null modem cable! Doom - My first exposure to true LAN gaming. Jackbox Games - Just like the above, the first one felt revolutionary. Guitar Hero and Rock Band - Still miss the genre! Mario Kart - Obviously.