I just finished Hotel Dusk: Room 215 and it is definitely going on my favorites list. Adventure game wise it on top with Monkey Island and Dreamfall. DS wise I couldn't put it down at all, which is way more then I can say about a lot of other DS games. Over all, it had beautify rotoscope animations, as well as a well strung together mystery story(those are hard to do, and still be good), as well as very believable characters. It didn't challenge me a lot, save a few puzzles, but for some people that a plus.
It is 10/10 with extra praise to the character design.