The laughter thing is interesting when you think about comedies. If you went purely on laughter as a way to measure quality in a comedy, then most people would hold the broadest and most appealing comedies to be the best. And, of course, everyone has different taste in comedy. It's the same with horror movies. Some people won't be scared by any supernatural films, and some of us are shaken by the worst of them.
As I said on Twitter, I don't find much to laugh at in Lebowski. I think Moore is perfect casting, and Bridges and Goodman have moments of genius too.
Apart from that, a lot of its elements don't really click for me. I appreciate the pastiche elements of the script, but I don't think it builds to anything in particular. That may be my biggest problem with the film; it seems to hum along for most of its running time without doing anything in particular, and without wanting to, either. You could probably make a case for the film being like this because the Dude is the character we stay with, but I can't fully buy into that.
And this is just personal taste, obviously, but most of the situations with Walter feel awkward to me, and not in a comedic way. I do love Buscemi's repeated "I Am The Walrus," though. And I can never get enough of Julianne's strongly vaginal artwork. ;)
It may be another case of something being overhyped and damaging my enjoyment. It's the sort of movie I can appreciate for certain craft elements and for how weird it gets, but it still doesn't do anything for me.
(I can also probably find some love for that soundtrack)