The Blue Ridge Parkway is spectacular in a car, especially in the Spring. It would be even more spectacular on a motorcycle, I’m sure.
My vote for second place would be John Pennekamp State Park at the top of the Keys.
Also a vote for the Silver Springs area near Ocala.
Having had a serious motorcycle accident in 1988 that made me a member of the Broken Angels Motorcycle Club, I decided to restrict my riding to four wheel vehicles. Several years ago I drove the Blue Ridge Parkway in my Navigator. It was great but, had I been ten years younger, I’d have done it on a BMW R 1200 RT. Oh, sweet bird of youth, how thou art flown.