In no particular preference order
1. Roller Coaster Tycoon - Great fun and learned a lot. Helped me decide my future career
2. Super Mario 64 - at 5 years old, I had never seen such vast and colorful worlds.
3. Super Smash Brothers Melee - Multiplayer mayhem at its finest. Helped get through awkward middle school years
4. Mario Kart Wii - Most addicting racing game ever. Over 600 hours logged in.
5. The Legend of Zelda: Majora's Mask - The only game here I initially hated, but once I figured the game out, one of the greatest games unfolded to me.