It is hard to tell which was the most succesful. Succesuful for who? if you the raise a lot sure the devs make a lot but the best are smaller coins that go up in value a lot. These normally have small ICO's.
I think we are talking about the most succesfull ICOs depending on our opinions, experience, analisys fundamental about the ICOs projects that has potential will be more more succesfull and gives us good profit in the future, of course our analisys must use valid data from the developer and official website of the ICOs projects.