If you enjoy challenging puzzles, then you must try Professor Layton and the Curious Village on the DS. The game is a series of over 120 puzzles set in an adventure style game. Many of theses puzzles are difficult, very difficult.
The European art style is reminiscent from old European cartoons from the 70’s and early 80’s. It works really well for the theme. Very cool, you get better at solving the various puzzles as you play through. Though I still am terrible at the ones where you have to decide who’s telling the truth, seem to better at the one’s involving shapes or math.