[johanbev]

The main difference between chess and Jeopardy is that Watson has to interpret ambigous (and awkwardly presented) "answers" and interpret what will be a suitable "question" to that. Both these two are really difficult. Watson needs a lot of natural language understanding across all lingusitic domains to even be able to search its databases and rule engines and what have you.

Chess, in contrast, is a totally deterministic game and the game state can easily be fed into a computer. That computers are able to beat humans at that comes as no surprise.