To me, it was Starwing / Starfox. Why? It was the first game I ever beat on my own ( Super Mario World was the second. ) , The easy route though but at 8, it was a pretty big deal for me. I had rented it about 3 times before and I can remember it well, it was the first weekend of Summer when I rented it again and this time I finally beat that bloody transformed Phantrom on Stage 6, only to fight Andross. I finally beat him and finish the game. Oh, the euphoria!
To this day, that game holds a special place in my heart.