I haven't played Skyward Sword yet, but it depends on what mood I'm in.
Ocarina easily has the weakest script of any of them.
Wind Waker has boring sailing.
Twilight Princess is an Ocarina clone with an improved script and clunky wolf combat.
It's a tough call, but I would say Ocarina is the worst of them. I value script above anything and Ocarina really has a clunker,