For me, Ecclestone is first with tennant as a close second. Matt smith has a nice character, but i think that he is being let down by the writing and the episodes, like how in half of the episodes, its not him who saves the day but the assistant, which can work but should only be used rarely, and there should be somthing that should stop the doctor from being able to help (the episode "42" was a good example of this)if this is used. For me, the assistant should be slightly less clever and the doctor should be slightly cleverer. But there are plenty of episodes to go before i can really judge him against the others, and the most recent episode was excellent.