Damn ... did a huge reply to this but my bloody computer crashed. So take 2 ... and paraphrasing what I wrote earlier:
Blimey ... I agree with freemars2259, and I'm Welsh too ... blimey ... must be the end of the world or something ... croeso i gymru (welcome to wales ... for those not in the know).
Yep ... no question about it, Dr Who is the greatest as freemars2259 says.
But its the ideas that make it stand out from all other sci-fi programmes ... forget about the actors (which people like or don't like or can't connect with on some level), the terrible special effects in the (classic) series [but when you find out how much money the producers were given to play with, you're amazed they made anything at all with it], the hammy acting (sometimes).
For instance, at the end of the Tom Baker era ... in the adventure, Logopolis, the entire universe is endangered by a wave of entropy ... now think about that for a moment ... the ENTIRE UNIVERSE is endangered by a wave of entropy ... now you do NOT get a bigger story line than that.
Also, the entire mythology surrounding the venerable Doctor and his race, the Timelords, is absolutely astonishing ... when you take in all the canon ... the books, the tv episodes, the audio plays, the comic strips. I found a time-line on the internet once regarding the entire canon, and it started out something like 30 million years BC (when i think the Doctor (not his real name of course) was born) and went far into the future ... and thats just the tip of a bloody enormous iceberg.
I'm sure its got even more complicated since then.
Anyway, rant over, except to say, if you don't like David Tennant ... well there's no hope for you
(check him out in a thing called "Taking over the Asylum" from the early 90s ... he'll tear your heart apart ... very sad stuff), and he is a wee bit manic I guess, but he's got phenomenal energy and seems to be really having a blast making it (he is a big fan of the series after all). Oh and when he goes into super serious mode ... well ... he gives Tom Baker at his best a hell of a ride for his money.
Oh and one other thing. I like to think of the whole Dr Who series as a sort of exercise in archaeology. If you think of all the adventures as actually happening at some time or other, as real events, and the tv series etc as a way of putting together a history of the Doctors (real-life) adventures using the resources given to the producers at the time ... you can sort of get round the bad special effects and acting problems