I think when he was still an active wrestler he brought instant credibility to the show almost single handedly and would be able to do so now if his health permitted. Especially when WWE decided to officially make Smackdown the B show during that time when they had Batista, Orton, and Cena the three highest profiled stars in the WWE, on RAW. Taker still made Smackdown seem somewhat credible, even though he was surrounded by guys who were talented but not booked as top stars(IE: guys like Edge, jericho, morrison, cm punk, rey mysterio, ziggler, christian, etc). Smackdown to me was Undertaker + all the work rate guys so it satisfied the old school fans/IWC fans like many of the posters on this forum to have arguably the biggest bad ass from the Attitude era + the work rate guys. Taker made Smackdown look legitimate because there was a guy who can probably beat everybody in the WWE including the RAW guys clean one on one. After he left, everyone just looked like B-level guys and it didnt help that they took most of the work rate guys and put them on RAW. Orton was not able to fill his shoes.