Such a hard question to narrow down just 5.
007 Golden Eye(N64) -Came out when I was in Elem. School. First FPS ever played.
Super Mario World (SNES)- It's what got me into gaming.
Bioshock - Upgraded my computer just to play it. Many good memories that time in my life.
Finaly Fantasy 8 (No not 7, 8) - Played countless hours in Elem. School with good friends.
Half Life 2 (PC)- Built a new computer for it, skipped so many classes in high school for it and skipped all periods the day it came out haha.