Much as I loved Monkey Island and loads of the old school Lucasarts adventures, I'm fairly certain the 'humour' I enjoyed came from the slightly oddball Tim Schafer, rather than Ron Gilbert.
In fact Tim Schafer is the comedy genius behind these games - I'm convinced of this. We should build a little shrine to him and wear tea towels over our heads and pray to him.
If you're pining for some of that old Lucasarts humour then you really have to play Psychonauts. It's available on Steam, it's incredibly funny, and it has deep and clever humour, and it only costs a few quid. In my opinion, it makes the new 'Sam and Max' episodic stuff look pale and uninteresting.
I can't wait for what double fine studios create next.