For its time, Super Mario 64 had AMAZING graphics. Everything was crisp and vibrant. When you saw Bowser for the first time in the game you thought "Wow! He's HUGE!" Each level had different landscapes and textures that made them truly unique. At one point you were swimming in quicksand in the desert and before you know it, you're dodging fireballs and trying to stay away from the lava.
My favorite level was Boo's Haunted House. Knowing that a ghost could pop out of any wall and kill you always kept me on edge. The level was always full of surprises! I know I jumped out of my seat the first time I walked near a piano. Overall the haunted house was easy enough to not get enraged but hard enough to always keep me on my toes and challenged.
(Boo's Haunted House)
Super Mario 64's clean controls, beautiful graphics, and fun, challenging game play kept me enthralled for all 120 stars (By the way, I FREAKED out in excitement when somebody told me about Yoshi :D). I've spent countless hours playing this work of art and it is easily one of the most memorable games from my childhood.