It's Funny Because It's True

Of course Ben Elton doing his tirade on the teapots that "always burn you" at service stations is not funny because it is just not true.

Surely Ben Elton's teapot gag fits this bill? I guess you mean an observation you haven't consciously formulated/heard before*. In which case I agree. One of my favourite bits in Seinfeld is when an annoying stand-up acquaintance of Jerry's starts doing really lame-o observational comedy routines (about dodgy shopping trolley wheels and stuff) and everyone loves it, including Kramer et al., who tell an increasingly exasperated Jerry he could learn a thing or two from him.

* like that BLOODY ALANIS MORISSETTE THING {sorry}

No, I think the thing is that pre-early-80s comedy was largely about either the comedian's personality/performance, or some sort of issue - - Robin Williams or Steve Martin in the first category, or Richard Pryor in the second -- things the viewer didn't necessarily relate to on a gut level. There was a sort of screen inbetween performer and audience. Observational comedy surely seemed stunning at first, in that it gave people license to talk about the tiniest details of everyday life ("What's the deal with those airplane peanuts?"), bringing the comedian down to the level of the audience, essentially. This makes things funny -- there's always something funny about devoting a great deal of analysis and importance to some issue that's completely unimportant and yet still a huge part of your everyday life ("Those things on the end of your shoelaces -- is there a name for those?").

Problem is, it's quite thoroughly played-out. Especially given that I think it's converted an entire age range -- everyone who grew up in the 80s or later, really -- into observational comics, or anyway people who amuse themselves greatly by getting really analytical about mundanities. (Sitcoms put the nails in: people really do relate to one another as if they're on "Seinfeld" or "Friends" tquite a bit of the time, which isn't the worst thing in the world, but makes that next observational standup guy look pretty dull.)

Further note: the huge rise in observational comedy surely came from comedians finding it a really, really easy source of material. I mean, you can just walk around doing your thing until something strikes you as amusing, and there you are.