If you're choosing between Kameo and COD2 I'd definately say COD2. COD2 is a better 'game' IMO, but Kameo has a LOT of playability and a LOT of different routes to go down. Where COD2 in a linear game, Kameo isn't.
If you want a huge challege and feel really good afterwards, then again COD2 is your man, but if you're wanting something that will last a little longer, has plenty of scope to go back "for another go" to try a new technique or better your score by doing something crazy, then Kameo is the one for that.
As for the keyboard to console. If you'd asked me when I got the 360, I'd say the mouse/keyboard wins hands down. Now, I'm not so sure, I'm starting to swing more to the controller.