The Phoenix Wright series is excellent. I am incredibly biased, but they're kind of point-and-click games where you have to gather evidence, talk with people, and piece together stuff. The writing is top-notch and it has some really great characters. The first game is still my favorite in the series (again, bias), but they're all generally very strong, with four or five cases per game. There's currently five games out, too, so they'd keep you busy for awhile!