No spoilers, because I know some of my Whovian friends haven't yet had the chance to watch the first two episodes of the latest season of Doctor Who, but I'm so impressed with the quality of writing from Steven Moffat (who also writes Sherlock, another must-see TV show).
Steven's brilliant scripts, coupled with great acting from Matt Smith (who plays the Doctor so well, I'm prepared to consider calling him my equal favorite doctor - if you're wondering, Patrick Troughton has always been the best Doctor, so far as I'm concerned) are so good, I'd have a hard time choosing between Matt Smith's Doctor Who adventures and Firefly, as my favorite TV show of all time.
How about you?
Which do you prefer, Firefly or Doctor Who?
Firefly by a shiny mile
The Doctor wins hands down
I love 'em both
Something else, which I'll mention in the comments