Colossal Cave Adventure 9+

Before there was Doom, Ultima, Rogue, or even Zork, there was... Adventure.

There were other text computer games before Adventure, such as STARTREK and WUMPUS, but this was the first of its kind; the first text "interactive fiction" game. It may seem outdated and quaint by today's standards, sort of like seeing the Wright brothers' original flyer parked next to a Boeing 747, but many of us remember it fondly.

The Origins of Adventure
«I had been involved in a non-computer role-playing game called Dungeons and Dragons at the time, and also I had been actively exploring in caves — Mammoth Cave in Kentucky in particular.
Suddenly, I got involved in a divorce, and that left me a bit pulled apart in various ways. In particular I was missing my kids.
Also the caving had stopped, because that had become awkward, so I decided I would fool around and write a program that was a re-creation in fantasy of my caving, and also would be a game for the kids, and perhaps some aspects of the Dungeons and Dragons that I had been playing.
My idea was that it would be a computer game that would not be intimidating to non-computer people, and that was one of the reasons why I made it so that the player directs the game with natural language input, instead of more standardized commands. My kids thought it was a lot of fun.»

— William Crowther