I haven't met a WDW dessert I haven't loved myself. It's too bad you can't get a decent cup of coffee to go with them.
In terms of restaurants that have a number of great desserts to choose from, I'll go with the Coral Reef and Chefs de France.
All the desserts we ordered at these restaurants were very good. From the Coral Reef, we had the Chocolate Wave, the Bailey's and Jack Daniel's mousse and butterscotch creme brulee. At Chefs, we had creme brulee, profiteroles with chocolate sauce and ice cream, and a chocolate mousse cake.