for me it was computer games, specifically Civ 2. Imagine playing that as a second-grader with zero English. But I had strong motivation, and ploughed through the game, dictionary in hand.
Same here. Either the original Japanese release, or the English fandubbed JRPG release for emulators. The choice was clear there; and my English skills skyrocketted with Chrono Trigger.
At least you had graphics. Zork I did it for me, I still remember my first word: "forest". Never could figure out wtf a "stiletto" is though, it wasn't in the ancient dictionary I had at the time.