“American Idol” seemed to be the way many viewers are going Wednesday nights, and maybe that’s having a toll on “Lost.” Or then again, maybe it’s too science-fiction for the masses. Many genre shows are struggling to stay afloat right now, and while “Lost” is keeping a mostly stable audience, it’s still not pulling in the audiences it once did, even last year. “Lost” earned a 5.9 rating/9 share Wednesday according to Fast National ratings from Nielsen Media Research. That was down more than 9 percent from the previous week, and finished behind both Fox’s karaoke contest and “Criminal Minds” on CBS. “Lost” did finish ahead of “Life” on NBC, which managed just a 3.3/5, according to Zap2it. There was no new “Knight Rider” available for NBC, which went with a “Biggest Loser” …