Probably doom/Wolfenstein 3D (the original DOS title, obv.)... That started the whole thing, but FF6 and 7 were also huge catalysts for it back in the day. I think FF6 on the SNES was the first game I was addicted to. I couldn't have been much older than 10 at the time.... I can't say that I really understood the plot, but I enjoyed it a lot.

FF7 and 8 were both fun too.

After FF 6, we got LTTP and that's also huge for me. I've fallen away from LOZ, because I don't want to pay the Nintendo tax....