This thread has been inspired by the fact that my flat-mate has only just got into The Sopranos, some ten years after it first aired!
For my part, up until a few years ago, I hadn't seen a single episode of Seinfeld, and only got into it via the DVDs after I'd run out of Curb Your Enthusiasm.
Also, BBC2 are due soon to air The Wire, some seven years after it started.
So, come on and 'fess up - what did you get into a long time after everybody else did! (TV, music, whatever).