Well, I have both games, and though they may seem similar by conceit, they are very different.
Kessen is a purer strategy game, in that you direct large amounts of troops and can (but don\'t need to) plan out your attack, who you\'re going to bribe, etc. It has gorgeous graphics, but you aren\'t as involved as a player. All you can do with your generals is do a special attack when you\'re hyped up. Even during a joust, you have no control. It\'s based on Japanese history, the Tokugawa regime.
DWII is based on Chinese history. There are large amounts of troops, but you don\'t really direct them from overhead. Rather, you take control of one general, and fight through tons of enemies, killing generals, falling back when you\'re overwhelmed, etc. It\'s more of a final fight type of game in 3D. It\'s probably more fun for the average gamer.
So the games are very different. Though I like both, I would recommend DWII over Kessen for most people. It\'s more interactive, and even the strategy elements of Kessen are kinda iffy. I still have no idea how to win battles by anything but sheer numbers in Kessen, though the size of the strategy book tells me it\'s deeper then I think it is. But DWII is a blast right out of the box, even if you have no idea at first what you\'re doing...