Something like this would be hard to do, especially how Adam wants it done. I would say it needs to be a comedic point and click game set around the plot of an episode new or old. Telltale or whatever company that speclizes in the type of games would do it.
To fit the R-rated nature of the sitcom itself the game should be rated M (and maybe by suprised AO). Lots of comic mischief in this game there should be. One level can be called (as a parody of beat the pinata) "Beat the Newman." The more you beat up Newman, the more points you get. This would make for a fun game. LMAO
Not only do I believe in the theory that most video games based on television shows and/or movies usually flop, Seinfeld was a great Tv Show....years ago. I really don't think re-hashing what was once great into a video game, will give those former fans of the show the desire to return let alone play.