In regards to old school adventure game, its not my favourite genre. But Grim Fandango is one of the high points of the genre. And I hope they take a lesson from machinarium. Gameplay wise machinarium is my fav adventure game of all time, in that it doesn't drive me insane through frustration.
If you liked Machinarium, you should definitely check out Daedelics other adventures, especially the ones produced Jan Müller-Michaelis. Edna & Harvey: The Brakeout is one of my favourite adventure games, probably my 3rd favourite after Simon & Simon II. They just recently released a sequel to it but no english version as of yet, its still lying around here, didnt find the time for it yet. Their newest one "Deponia" seems to be really good aswell.