WITH SO MANY SHOWS BEING INTRODUCED this month, it might be a good time to explain the new criterion I am applying to series. I got the idea, like I get most of my ideas nowadays, from watching the O.J. trial. When Johnnie Cochran cross-examined LAPD officer Robert Riske, he asked him to identify another policeman from an obscure photo that showed little more than a beefy arm. To prod Riske’s memory Cochran asked if any of the cops at the crime scene were “particularly ‘buff,’ ” as in especially muscular. That phrase so captured me that I have added it to the checklist of qualities I use to measure every show. (You’ll see how this works as you read on.) Most shows would not be affected by this sinewy new standard. Clearly, though, the stock of programs like Baywatch and American Gladiators has just soared, while Roseanne’s has plummeted.