I, for one, will admit that for all their flaws I like Full House, Who’s The Boss, and The Cosby Show.
…like the show itself.
Bazinga.
I’m trying to figure out how it’s meta - I’m gonna need a diagram. 
Big Bang Theory is a show ABOUT geeks written by normal people for other normal people.
XKCD is a comic strip written by a geek for other geeks.
If you want a show written by geeks for other geeks you’re better off watching Venture Brothers reruns.
Doesn’t that support my point? Real scientists act nothing like the supposed scientists in the show.
I realize this is nothing unique to The Big Bang Theory. Most professions in sitcoms are unrecognizable to people in those same professions in the real world.
When XKCD tries to be funny it is usually funnier than TBBT, but TBBT is always trying to be funny and occasionally succeeding. TBBT is an ok show. As others have said, it’s essentially a standard sitcom in geek clothing. It’s not a great comparison though, since many XKCD comics are not trying to be funny. (They are still usually interesting.)
You could change TBBT to be a show about insurance agents or cooks instead of scientists+Howard without fundamentally changing the structure of the show. While I think it’s an ok sitcom, it will never transcend the standard sitcom formula. It’s geekiness is a veneer.
The geekiness of XKCD is deeper. A (geek) friend of mine once told me that XKCD speaks right to his soul. While I don’t think I’d put it quite that strongly, I agree with the basic sentiment. The author of XKCD is a geek. His comic strongly reflects that. There are many XKCD comics that aren’t funny ha-ha, but are funny that’s-so-true-I-can-totally-relate. Others aren’t funny at all, or have a very small amount of humor, but are insightful.
Two of my favorites:
Don’t fire until you see the whites of their eyes …
I think this one is funny haha.
Wisdom of the Ancients
This one is funny to me because I’ve been in that exact same situation multiple times over the years. I wouldn’t expect someone who can’t relate to it to find it amusing.
The next time I see something funny in the Big Bang Theory will be the first. It doesn’t matter if it’s about nerds or not; it’s a very mediocre sitcom.
XKCD is sometimes hilarious, and sometimes quite poignant. It actually engaged the emotions. The Big Bang Theory is just another 22 minutes of corporate garbage.
XKCD had some funny early strips but now it’s downright stupid. (I’m a staunch believer in what the XKCDsucks blog usually says - that XKCD lacks any good humor structure or jokes, and people only like it because they understand the nerd reference and feel intellectually smug. Congrats, you know what Higgs-Boson is! You’re so smart.)
I didn’t watch Big Bang Theory all that much, but my housemates watch it a lot and so I’ve been seeing more of it. It’s alright, for a sitcom. Some good jokes here and there.
Neither.
Big Bang Theory is painfully unfunny.
XKCD doesn’t appeal to me
This is one of my favorite strips, and I’ve since used the example in similar discussions. Unfortunately, you can’t get a signed version of this strip.
ETA: It has also given me an interest in Canadian Surrealist Porn.
I laugh at The Big Bang Theory.
I think XKCD is clever but very, very rarely (if ever) actually funny. It may have made me smirk but never as much as giggle.
Guess which way I voted.
I went with the top one, but I could have just as easily went with the bottom one. They both are sometimes funny and sometimes not, and I can’t be bothered to quantify whether they are more often funny or not.
I do know I see nothing wrong with either type of humor.
Big Bang Theory is consistently amusing, but rarely all that funny. XKCD is more inconsistent, as it can be great or terrible depending on the strip.