I've not been a Who fan for long, only since the new series launched. Christopher Eccelston was alright in giving the Doctor a dark and broody quality, following everything he went through during the Time War, but for me David Tennant was just spectacular.
I've recently had a rewatch of my boxsets, which has made me miss Mr Tennant and long for a new Who fix, so I watched the latest BBC 1 eps and remembered just how much I dislike Matt Smith in the role. He comes across as too goofy to me, which isn't what I'd comes to like about Tennant's Doctor (yes, he had his lightsome moments, but I could still take him seriously as the last of the Time Lords).
I will say one thing about the second half of season 7 is that the TARDIS has a far better design.