While AS pursues the best lines, here's a vote for one movie with the greatest number of quotable lines, including the following favorites:
Dr. Venkman (Bill Murray): "Back off, man. I'm a scientist."
The Dean: "Your theories are the worst kind of popular tripe, your methods are sloppy, and your conclusions are highly questionable."
Dr. Ray Stanz: "Personally, I liked the university. They gave us money and facilities, we didn't have to produce anything! You've never been out of college! You don't know what it's like out there! I've *worked* in the private sector. They expect *results*. "
...the list goes on. Including, "Yes, it's true. This man has no dick. [rumble] Well, that's what I heard!" and "Lenny, you will have saved the lives of millions of registered voters.":