I would imagine there will be a lot of opinions on this, and will depend a lot on how people play the game.
in my opinion the best ultimate buildings are the early ones (you have them longer!) and the Ottoman aqueduct is superb with +2 bonus along with the standard +2 health.
in my opinion the best ultimate buildings are the early ones (you have them longer!) and the Ottoman aqueduct is superb with +2 bonus along with the standard +2 health.