What can I say about Doctor Who that hasn't already been said? It's the show that inspired so many other great things after. It influenced Star Wars with R2-D2 and C-3PO. The Daleks and The Cybermen were the original versions of the robotic duo basically.
I don't know of a show that is even more epic than this golden gem of television history. Of all the doctors, I would have to say that my top three favourites would be Tom Baker, Peter Davison, and David Tennant. I hated seeing him leave the show.
I love not just the new version, but also the classics. Doctor Who is an all-round fantastic show, and surprisingly moving too.
If you haven't seen Doctor Who yet, do yourself a massive favour and start with the David Tennant episodes, and welcome to the greatness that is the finest science fiction show ever created.