I found the choices really difficult to make but gave it a shot. My top 10:
1/ Gabriel Knight 2: The Beast Within
2/ Day of the Tentacle
3/ Gabriel Knight: Sins of the Fathers
4/ Monkey Island 2
5/ Noctropolis
6/ Eco Quest
7/ Amazon
8/ Darkseed
9/ Space Quest 4
10/ King's Quest 5
I chose these games as they were what I played as a child from the age of five onwards. I just remember the warm and fuzzy feelings I got when I played them all those years ago.