If you're an American in your mid-twenties and you don't have an oregon trail story from when you were in primary school, well then you missed out. I may have to go out on a limb and say best educational game ever.
Seeing as how I first learned how to program on the Apple IIe, I have fond memories of that platform. Especially little games I wrote myself, inlcuding a program that played the first measure of Beethoven's fifth and at the end asked "Would you like to hear it again?" if you said yes it started playing, if you said no it said "Too bad sucker, classical is good for you! Listen up!"
I still play both Fallout and Fallout two regularly, and I loved both X-wing and Tie Fighter, but what I'm most astonished is that no one has mentioned Monkey Island!
I loved the Adventure Game genre, it seems isn't flashy enough for todays developers to produce any new titles but back in the day I loved all 4 Monkey Islands, Sam and Max hit the Road, the old Indiana Jones stuff, Day of the Tenticle, and Full Throttle. Man those were some good games.