Do you need 10 great ECs to get into top colleges?

Less is more. Very unique and very strong will stand out more then random names or clubs. You want things that you are involved in for 2-4 years. The longer the better. Sure put down a club or two you tried out etc.

Colleges want all sorts of kids. They like ones that are active on their campus. From your essays to your Ecs they get a picture of what type of student you will be on their campus. You are painting a picture for them to see.