Though it once stood proud as a majestic and much-celebrated Super Bowl adcaptivating an audience of millions with its sleek, seductive images and stunning production valuesa television commercial for Doritos was reduced Wednesday to occupying a feeble 30-second slot between segments on The Price Is Right. 'It's tragic to see an ad fall so far so fast,' viewer Bob Crumbley said of the corn-chip spot, which just last month was beloved far and wide for its sly and good-natured humor, but has since become nothing more than a meddlesome obstruction to the Showcase Showdown. 'What a humiliating way to go.' The ad is scheduled to fall even further from grace next week, when a pathetically truncated 15-second version will air during a rerun of Judge Joe Brown. 