Must say - I'm a Tennant fan through and through.
But Matt has made the role his own, and good luck to him. He waves his arms about a lot (but that's not acting - have you seen him on chat shows? He does the same!)
He definitely reminds me of dear Pat Troughton (MY Doctor) in certain respects, and carries the role very well.....although he uses that Sonic Screwblaster FAR TOO MUCH! (but that's the writer's fault)

In answer to the question: NO he's not the best actor on TV.
YES: he's a good actor

His looks make him ideal for something like Doctor Who

Many of the actors you see in soaps are very much of the type "what you see is what you get". They have a limited range of ability and once they leave a soap or series many fail to find an acting job on TV again. And even if they do it's a type cast role playing exactly the same character.

As for the Doctor, you say wacky, I'll say a poor attempt at a slap stick style of humour that fell out of favour when the music halls closed. It lazy script writing and acting and often used as a mechanism within in an episode to hide a weak plot. When the script writer cannot think of a good explanation for whats happening on the screen they resort to:
i) Sonic screwdriver to miraculously to open all doors/fix all faulty electronics/reverse the polarity of the flux capacitor etc.
ii) A character saying "run" followed by a pointless filler section where all the main characters run around like headless chickens. These days it seems to be in every episode.
iii) The main character "hamming it up" being wackey
iv) Inserting some hidden clue to keep the Dr Who geeks happy. A handfull of geeks will put forward all sorts of theories from these clues but the majority of the audience couldn't care less.

As for best actor, hes not even the best actor in the series. Most of the one off featured guests are much better actors

He great at some types of roles, but not others, and seems to be most suited to playing more eccentric characters. I thought he was really good in Christopher and his kind, and of course he is brilliant as the Doctor, but in anything that involves doing a cockney/London accent he is less convincing.