Roller Coasters are the ONLY good reason for going to an amusement park. I love Cedar Point solely for the sheer amount of coasters there. Two of my favorites are The Beast at King's Island, and Superman at Six Flags New England.
The Beast is a pretty decent roller coaster. It's the fastest, highest wooden roller coaster in the world, if I remember correctly. They have another The Beast roller coaster there now that is faster than the original.