Along the lines of your favourite 80’s game, your favourite DOS game. Ever. And if they made a Windows version, it doesn’t count, only games made soley for DOS (my personal favourite OS) count.
My vote: The Commander Keen Series! I love them! You?
Scorched Earth. The mother of all games.
Aces Over Europe. Best Game EVER.
The Zork series. Great writing. I now have them on my Palm Pilot.
Thomas Disch’s Amnesia
A lot of people forget about that one.
Technically, Doom is a DOS game since it runs in DOS mode, there’s my vote.
Tetris seems to require some mental skill.
But its not good for long periods.
Lode Runner!!! (this was back in 1984-85ish)
I would spend hours upon hours getting to new levels and creating my own levels. I even have the Windows 95 version loaded on this 98 machine.