Personally, I'm not convinced their styles would work that well together. James berates games for mostly legitimate reasons. He exaggerates for comedy's sake, of course, but in general, his complaints are well-reasoned. Yahtzee, on the other hand, tears games apart for the sheer entertainment value of it, and thus doesn't always field his complaints in a completely rational way.
Also, E.T., while notoriously bad, is probably a little thin for two separate entertainers with two separate styles to work off of in tandem.