You probably saw the game before on other forums. I randomly chose 15 of his movies.
Each has 15 points. Add one, take one.
Let's see which of these Robin Williams movies is the best :)

Dead Poets Society 15
Jumanji 15
Good Will Hunting 15
Flubber 15
Father's day 15
The big white 15
Good morning, Vietnam 15
Night at the museum 15
What dreams may come 15
Jack 15