Hard for me to choose, but deep down I'll have to say: Super Mario Bros. 3
I always feel like I keep forgetting how awesome that game was. I remember playing it a lot with my mom back when she actually had an interest for video games. I remember using my game genie to beat the game a few times. I figured out how to get one of the flute's in the first world, and my mind was blown away when I found out years later how to get the second flute in World 1. I always grabbed the second flute in the second world. Finding out about that hidden path and getting the frog suit was amazing as a kid. I felt like I stumbled upon a hidden treasure.