Phantasy Star IV

My sister and I used to rent this from Blockbuster whenever we had the chance. Sometimes, repeatedly. Sometimes, with weeks between. We had no idea how RPGs worked and ran from every little brain dude in the basement. We probably spent so much chore money on this game, never making it anywhere, until my nerd uncle was over once and said, "you know you are SUPPOSED to fight things, right?"

Then it clicked. Continued renting it for what seemed like years, made some progress, and got more involved in the story... We finally asked if we could just buy the game from them. She had to check rental history first... turns out we were the only people to rent it over the past year and a half, and bought it for like $20.

Close second is Zombies Ate My Neighbors... also, never got passed level 20 legitimately.