I checked out the Pirate Bay's top 100 section the other day, and was astounded to see that The Big Bang Theory was the top TV show.
A lot of sitcoms aren't funny, but Big Bang Theory is like being held down by your older brother while his spit drips on your face.
Maybe it's supposed to be ironic? Like it's so bad it's good?
In high school my friends and I had bad-movie nights, where we'd do our own Mystery Science Theater. Is it like that? Do friends get together and smoke pot and have a Big Bang Theory marathon where they make fun of how terrible the jokes are?
It's 20 minutes of cheap entertainment and it's still better than a bad sitcom that is not about geeks.
Maybe it helps that I can't really identify with the characters because everything is so American (and I'm not)?
(it's hard to explain, I never exactly realized which parts of US series--comedy or not--were "show" and which parts are just how US culture is, before I visited the USA. Maybe imagine all the tiny things that are slightly "different" when you watch a European series? Related, there's probably a lot of scenes in European series that make me cringe because they're a little bit "closer" than for a US viewer who maybe assumes it's just part of the show's quirkiness. Dating culture is one of many examples)