Russell T. Davies, Billie Piper and David Tennant made Doctor Who quite non-nerdy by bringing in a HUGE female audience. When your audience is 50% or more female, you automatically increase the dating possibilities and reduce the nerd factor. That's why Trek will always be nerdier than Who or Star Wars...
I think that we have to look at each of those shows as a whole, though. Yeah, RTD has done wonders for Doctor Who lately but taken as a whole it is a giant nerd-fest. I would tie Doctor Who and Star Trek as equally nerdy* because they are both (more often then not, I think) cerebral. Star Wars, on the other hand, is candy for the brain. Quite often yummy candy but still a lot of empty Calories.
*If we're going to use Doc's female audience factor then it is fair to point out that Star Trek has always had a huge female fan base.
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(runs away...)
*If we're going to use Doc's female audience factor then it is fair to point out that Star Trek has always had a huge female fan base.