Alon-zee, he's a fresh athletic match-stick man who made all the fan girls scream. Never have I enjoyed a character performance as much as Tennant as the Doctor. Conveys a lot of emotional depth and displays flamboyantly excessive comedic charm, not to mention the regular charm, which again he has an excess of.
David Tennant's real life has some interesting and unexpected twists worthy of the show's intertwined web of plots.
David's wife, Georgia Elizabeth Tennant, played the role of Jenny in the episode The Doctor's Daughter. Jenny was in fact, David's Doctor's daughter (born of a DNA sample taken from The Doctor).
Whilst Georgia's surname if remarkably similar to that of one of the show's writers, Steven Moffat, she is in fact the daughter of The Fifth Doctor, Peter Davison.
Her mother, Sandra Dickinson, is also part of Geek Lore, having played Trillian in the original TV adaptation of The Hitchhikers Guide to the Galaxy.
Though not an official Doctor, Mark has appeared a number of times in the official series:
as Professor Richard Lazarus in The Lazarus Experiment.
as Danny Boy (a spitfire pilot) in Victory of the Daleks and A Good Man Goes to War.
as [Gantok][1] in The Wedding of River Song.
Though not part of the TV series, this story features Paul McGann's Doctor, tying it into the canon. Other characters were played by Simon Pegg and Jessica Stevenson (Tim and Daisy from Spaced), adding additional Geek Lore value to this production.
Though he only played The Doctor as a guest in Matt Smith's Doctor's episodes, and had not believed himself worthy of the title The Doctor, he has been acknowledged as an official Doctor in the television series' storyline.
Whilst John Hurt's Doctor is a unique character (i.e. he's not standing in for a previous actor), he has only appeared as a guest in the current canon.
Georgia Moffett played the role of The Doctor's Daughter in the episode of the same name. In real life, she's Peter Davison's daughter, giving him and additional claim to being The (de facto) Doctor.
Whilst Peter Cushing's doctor had his own character and played the title character (as opposed to being a guest in another actor's doctor's episode), he never appeared in the TV series.
Hugh Grant is a person whose charming enough to be a perfect fit for our titular Time Lord. A lot of fans (still) want to see a canon Doctor played by Grant.
Whilst Richard played the role of The Doctor (as William Hartnell's incarnation character) he did not have his own interpretation of The Doctor, or his own season.
His credentials as an official doctor had been in dispute, as he appeared in a film but not the TV series. However, in The Day of The Doctor his role in this time stream was officially acknowledged.
In addition to playing The Doctor, Peter had previously played the role of Caecilius in the episode The Fires of Pompeii, an episode during David Tennant's reign as The Doctor.
Appeared as Walter Simeon and/or The Great Intelligence (which manifested itself in the form of Walter Simeon) in the episodes The Snowmen, and The Bells of Saint John.
Too much of a new age hipster with his timey-wimey space-wasey easy going philosophy. Although matured in his later years, Matt Smith couldn't sell emotion the way his predecessor (Tennant) could.