My friends were really into Dr. Who when I was in high school. I tried really hard to like it but I just can't get into Sci-Fi. I know there are a ton of Dr. Who fans though.
I've never watched much of the Classic Series (which ran from the 1960s-1980s), but it's the New Series that I love, which started in 2005.
Doctor Who isn't overly sci-fi though. I mean, in a recent episode, The Doctor described time travel as:
"People assume that time is a strict progression of cause to effect, but *actually* from a non-linear, non-subjective viewpoint - it's more like a big ball of wibbly wobbly... time-y wimey... stuff. "