Tom Baker will always be top of my list. I was watching Doctor Who on PBS since I was a baby, and Baker's episodes always were the most prominent in my mind when I thought of the Doctor. However, it is hard to pick a favorite, since I enjoyed something different about each one.
Hartnell, Pertwee, and Troughton would be close seconds; in no particular order. These three established so much of who the Doctor was and all struck a great balance between caring elder and crochety, old know-it-all.
I've also always had a soft spot for Colin Baker, since he got such a raw deal. He wanted to go with a darker kind of Doctor, which didn't seem to resonate with people after Davison's Doctor who was about the sweetest person who ever existed. I really wish they'd gone through with the idea since I think there was a lot of potential in it, but it didn't happen.
Sylvester McCoy was great too. His episodes often got pretty cerebral, i.e. Ghost Light and Curse of Fenric. He also brought a little bit of mystery back to the character.
Eccelston and Tennant didn't thrill me too much. They both did a fine job, and it was more the storylines that left me flat than the actors themselves. The "Doctor in love" junk had me gagging from the outset, and the more attractive-looking Doctors sorta made me uneasy with the series.
Up till then, Peter Davison had been the "prettiest" Doctor, with the rest being either older and/or kinda goofy looking. So Eccleston's cool dark clothes and Tennant's stylishly messy hair had me rolling my eyes a little. Of course there was the shovel loads of angst added to the show thanks to the "last Time Lord" angle. Angst is something I enjoy in very small amounts, and the new series (Tennant especially) overdosed me on it pretty quickly.
Matt Smith looked to be more of the same, but really surprised me once he got going. No more companion romances, thank goodness. Amy and Rory have ended up pretty awesome. And the angst seems to have been dialed back quite a bit as well; even with the continuing plotline of the Doctor's future death.
So, of the new series, Smith has been my favorite. But all the classic Doctors will always rank tops for me. But that's how it usually is. Almost everyone's favorite Who is the one they started with.
