If you liked Hotel Dusk, its sequel
Last Window seems like an obvious choice (it's just as good).
Ghost Trick, from Ace Attorney creator Shu Takumi, is also a brilliant DS game (and now ported to iOS).
While we're on DS games, I can also recommend
Time Hollow (fantastic story, a bit light on gameplay) and
999 (very wordy and requires you to replay the game numerous times to find the "good" ending, so it might not be for everyone, but I loved it).