The first? They were probably some of the most famous early ones, but they were not the first. That honor goes to Colossal Cave by most accounts.Originally Posted by Flack
(I also seem to recall that the license holder for Mr. Adams's games is still selling them online.)
There are lots of high-quality freeware amateur "interactive fiction" pieces out there. I've heard lovely things about Photopia.
I highly recommend Rematch, a particularly ingeneous use of the medium, in which you have an opportunity only to type a single command before you or your friends die in a tragic car accident. Such a satisfying game.