Boy, both are real stinkers. Fulton's gets some good notices, but the prices are too outrageous - the service too uneven - to recommend having a meal there. You might luck out and eat some good grub, but better seafood is available at Narcoosee's.
As for Capt Jack's...well, it gets my vote for worst restaurant in WDW. We had a meal here last month. After an hour wait (not a problem; it was a Saturday night, so we killed some time walking and drinking), we were seated and treated to the most grotesque dinner I've eaten in a long time. The seafood scampi was literally inedible: an unidentified orange goop poured over cold pasta. The service, however, was excellent. Our server was so cool that she acknowledged, "If I were you, I'd stick to drinks and appetizers tonight...."
I'm disappointed DTD has no decent sit-down restaurants.