I remember playing Oregon Trail on an Apple ][ in the "computer lab" during my brief public school incarceration. When my dad got an IBM clone back in the day, I played Where in the World is Carmen Sandiego and OutNumbered! along with some other geography, history, and math games. My sisters played Reader Rabbit and Richard Scarry's Busytown a fair bit later on.
My first real game was probably the version of Descent bundled with a sound card.
MECC made I several versions of Oregon Trail, the last one for one of the later revisions of the II (or maybe it was an early Macintosh) had the best hunting minigame. You could mow down the entire animal kingdom with rapid fire. Of all of their games though, I ended up playing DinoPark Tycoon the most, but by then I was playing at home. It was a fantastic game and birthed a huge strategy genre. I had a pirated copy of Carmen Sandiego and could never quite figure out how to play or make it fun.
Descent was so good. I didn't play a ton of it but I ended up playing its N64 clone Forsaken for many hours. Mechwarrior 2 was the first real 3D game I got into. I can remember being amazed at its limited and low resolution texturing.