Here's my list of the top 5 AGS top 10s of all time! Actually, I could only find 5 in a brief look on google... and they're not by any means AGS-exclusive. In no particular order:
CaptainD's epinions top 10 freeware adventures list
Independent Gaming's 2006 top 20 freeware adventures list
Gaming World's top 10 AGS games list
Rampant Coyote's top indie graphic adventures
My own 10 top AGS series list
Please let me know if you find any other top 10 lists!