I started reading Sherlock Holmes as a kid, and I've read most of 'em. So I can legitimately claim to be purer than thou.

And yes, Jeremy Brett's Holmes is definitive. It's a faithful rendering of Doyle's written descriptions of Holmes, and writing about him. (A pretty good second is a 1940s grainy serial that shows up occasionally on PBS, can't remember the title.) You're guaranteed to like Brett's portrayal to the exact degree that you enjoyed reading Doyle's portrayal.

But I thoroughly enjoyed the first two seasons of Benedict Cumberbatch's Sherlock, and thanks for reminding me I should try to watch them again before the third season starts soon. The fidelity of Cumberbatch's portrayal isn't an issue for me, and in fact it would be bizarre if he played it like Brett, given the displacement forward in time a century or so. The very familiarity of Holmes makes the intellectual puzzle work: How would such a well-understood quasi-historical (fixed in time) personality interact with our modern world?

I was hooked in the first episode, when Sherlock is at a crime scene, and a policeman bitterly mutters "psychopath!" behind his back. Holmes loudly and angrily declares "I am not a psychopath, I am a high-functioning sociopath! Do your research!".

Personally, Cumberbatch's Sherlock seems like an Asberger. That was the consensus I found on a forum for sociopaths (true, could I make that up?) when for fun I searched for that line. But the scene illuminated a huge difference in how moderns look at the world: We're conscious of psychology; Freud stands between us and Sherlock; and we're not shy about tossing around psychobabble at the drop of a slight.

And in that Cumberbatch is consistent with canon, I think. Neither Doyle nor Brett ever portrayed Sherlock Holmes as a cuddlebear. In our language he might be called a "sociopath", in their times he'd be "that cold, arrogant bastard". Displacing him to the 21st century highlights his maladjustment.

Or maybe it's just Benedict Cumberbatch, who seems to be taking over the world. I recently saw Star Trek Heart of Whatever, and thought that it was unworthy of Cumberbatch, who seemed to be hobbling his talents to avoid embarrassing the other actors.

So don't choose one as the "best". Enjoy all the Sherlock Holmes that the universe can produce.