I just really don't like the Eccleston dude. I've never seen his Dr. Who, but I don't like him in anything else.
I thought he was brilliant in Shallow Grave. His character wasn't all that likable, but then again, all of the characters were pretty much jerks. You felt sorry and repulsed by all of them at different stages.
I recently saw him in eXistenZ, though his character was a bit of a bore (which was admitted in the story as well, which was interesting).
He's an interesting Doctor, though he is not as whimsical as Tenant and Smith. He's cavalier about what's happening, but he also has a bit of a callous side to him.
I would say that Tenant and Smith are more fun.
I'm not familiar with the previous Doctors, though I have Netflix now and could remedy that.