Back in early 2002, Misty & I put a timeline of interactive fiction together, covering events from 1945 through the end of 2000. We took many of the notable adventure-game-related events of the last fifty-five years and put them on a poster.
We had the timeline printed; unfortunately, we don't have any more available. We do have images of the timeline, as well as a list of all events that are on the timeline. Feel free to peruse them; in the future we hope to make a PDF of the timeline available for download.