I voted Tom Baker [you never forget your first Doctor] but I have been greatly impressed with all three of the nuWho docs and would have a hard time picking between them. I've also seen only a couple of Colin Baker and no McCoy, and haven't watched McGann since the movie was first broadcast. I'll be remedying all of that soon.
I also only saw Hartnell and Troughton in broadcasts from the late 80s over here... and i like Pertwee a lot as well.
As has been noted, this is NOT easy. All of them have things i like.