A lot of print comics are about people with superpowers fighting crimes and monsters and things from space. That can all be mainly traced back to the huge popularity of Superman. A lot of webcomics (but I would argue by no means an equal portion) are of the 'two gamers on a couch' genre. This can be mainly traced back to the huge popularity of Penny Arcade. Pale imitator Ctrl+Alt+Del shoulders some blame too. Interestingly, Penny Arcade is the only webcomic of this genre that has ever really managed to be consistently funny. I suspect an element of this is how easy such strips are to draw. The other reason is that it's pretty hard to get such comics published in regular avenues, combined with the fact that on the internet there is an obvious natural audience for comics about computer-based subjects. You'll also find a lot of comics about subcultures, a lot of comics about angsty teenagers and a lot of comics about furries, for these same reasons.
I'd question that 'all too many webcomics' line though. Maybe that was true a couple of years ago, but, I still doubt that actually. I have 28 links in my 'webcomics' bookmarks folder, representing a variety of webcomics both current and past that I read/have read/whatever. Of these, only two could be said to belong to this genre. These are the aforementioned Penny Arcade and VG Cats. A couple of others (XKCD, Orneryboy) have geek references of varying strength, though only XKCD ever really bases itself on this. There is also one (Goblins) that is essentially set inside a game of Dungeons and Dragons but, meh. The rest of them are about a pretty wide variety of things, everything from high school relationships, to gay vampires to the comic doings of space mercenaries and ninjas practicing medicine. Of what I would loosely call the 'ten best webcomics', based on sheer fucking personal bias (Achewood, Scary Go Round, The Adventures of Dr. Mcninja, Nothing Nice to Say, Dinosaur Comics, Penny Arcade, XKCD, Perry Bible Fellowship, Goats, Girl Genius) only one matches your description, though Nothing Nice to Say has kind of the same dynamic.
As for your contention that such comics are unoriginal because of their outdated references, umn, do you read any political cartoonists? I've got collections of things like Nature Notes, Giles and If... which I still find amusing despite the fact that all of the references are out of date, in Giles case up to 50 years out of date. This is because GOOD comics can work around being too much of their time by having strong characters and simply good humour.