To add to your list, Machinarium is an absolute masterpiece. Beautiful hand drawn art, and some of the best puzzles in the genre (IMO). Anything from Amanita Design is worth playing, but it takes the cake.

And they announced the sequel just a few weeks ago!

My favourite Amanita games are the Samarost series. Something about the lack of dialogue, devious puzzles, quirky humour, and unique aesthetic combining sci-fi with a world of moss, wood, and weird junk.

Creaks was also excellent, albeit a very different vibe. I couldn't quite get into Phonopolis, although the art direction is stunning.