Grim features better writing, a better script, a better premise, better puzzles, and I dare say better characters. With Grim, I have a latching on to the characters I met and I would replay the game any day of the week. In fact, I did so twice in the past week. Oh Grim...

Although..Monkey Island DOES have the SCUMM bar.
I'm not saying Monkey Island is a bad game, but for me, Grim Fandango makes every other adventure game I've played look almost sophmoric. I'm not sure if that's hyberole or not, but it just clicked. Grim Fandango being made into a motion picture would give me a heart attack, I'm sure, because the potential is just sooooo there!
I need to play Monkey Island 3...the graphics look amazing..