You guys are touching on a very important point IMO. There are many changes between the tone of MI1, MI2 and CMI. Yes, Ron is involved in the first two games, but even between them there are some changes in atmosphere, plot tone, and character personalities that have always bothered me.
To me, the first game is about mistery and exploration. Beggining with the game's title - what's "the secret"? Most of the time, you explore environments alone and don't know what lies ahead. Getting into the giant monkey head or getting the navigator's head even gives you a bit of horror. The soundtrack reinforces this - exploring the forest in Melee, talking to the Voodoo Lady or arriving in Monkey Island makes you tense for the first time.
In this game, Guybrush is just a regular guy that is anything but a pirate. Elaine is a brave woman who has always had everything under her control and likes Guybrush precisely because of his innocent looks. Lechuck is scary, kills pirates and likes "hot winds of hell blowing in his face".
In MI2, Elaine was the same character, but Guybrush had lost his innocence. Now he has facial expressions, makes more jokes and has a goofy humor. He is no longer a dreamer, but a selfish pirate who tells everyone what he has done and what he will do.
After that, in CMI, EMI and TMI Elaine was just a generic damsel in distress, rescued by Guybrush, mighty pirate, and Lechuck has become a non-threatening cartoon villain. I love CMI and what Bill Tiller did, but always have missed the darker tone of the first two games.
I wonder what atmosphere we will find in RMI. What do you guys think?
These points were discussed by Ian Danskin on the part 3 of this video (after 12:50):