Gamespot has recently added Day of the Tentacle to their list of Greatest Games of All Time. They love it.
LucasArts pioneered a brand of adventure game in which you could never die--you would just get stuck for a while if you couldn't figure out a puzzle--and Day of the Tentacle is a perfect example of this carefree, frustration-free style of gaming. This is a genuine classic--very few games have matched or exceeded the quality of Day of the Tentacle's production.Check out the whole writeup as well as some cutscenes and other screenshot type goodies here. They also included Grim in the Best Evar list a few weeks back.