Try something like
Grim Fandango also by Lucus Arts. I loved that one. I've also heard of
Full Throttle I've never played Sam and Max or the Tentacle, but I'm interested in looking into them. I don't know if you consider Myst and Riven to be adventure games, but they could probably be thrown in.
The whole adventure genre kinda died out 5-10 years ago, but I'd love to see a revival of it because I miss that style of game. It took less dexterity and more creativity. It also had a great deal more humor. I would love to see what an adventure game would look like in one of the 3d worlds that the developers have engines for and systems to run them on.
Another curious point, upon doing a google search for "adventure games" I came up with this:
http://www.adventuregamestudio.co.uk/ It is a website where you can design your own adventure game.
I'm finally back for the summer, although hopefully I'll spend a little more time away from this screen.