I don't think any of them have a super romantic feel but I get what you are looking for and I would say that several are tied. I can't comment on staying there but I do visit them often to eat and shop.
The Grand Floridian is the most posh and very old school. But it does remind me of grandma's house or a fancy retirement home. It just depends on what your tastes are like. While waiting for my tea reservation in the lobby I saw a couple of older folk sleeping and hardly any children. It is beautiful though.
Polynesian is beautiful as others have said. At night it's really lovely with the tikki torches and the beach is beautiful. The pics of the rooms here look so-so to me. But I've not been physically in one. Also, there are a lot of children here and it can get noisy. But it would still be one of my top choices for you. You can get "lei'd" before you ever make it to your room.
Wilderness Lodge is a great choice if you like mountains, forests, wooden furniture, and the great outdoors. I'm not even into that stuff (more of a tropical girl) and I still felt this resort was breathtaking. It's worth a visit even if you don't stay there.
Animal Kingdom Lodge is very African and also breathtaking. I've actually been in the rooms on this one and there is something to be said for chilling on your balcony watching giraffes and zebras walk by.
I would consider any of those equally. It just depends on which theme appeals to you more.