Commander Keen: Marooned on Mars. My Dad had an IBM machine that booted up in DOS, and he installed a bunch of games on it for us. I played every Commander Keen game (including Keen Dreams), Wacky Wheels, Oregon Trail. Sim City, and Sim Ant on that machine (although I think I needed to boot up Windows to run those last two).
I don’t know where my Dad got them, but they were pretty much all Apogee games, so he might have order them directly. I was really young, 4 or 5, so I didn’t really ask for them. My Dad would just install them for us and create directory shortcuts so we could load them easily. Part of how I learned to type and read was spelling out, “keen4” and either getting the game to load or, “Bad command or file name.”