Only a week ago I deplored the wretched "Scooby-Doo" as a blight on the nation's theaters. My fellow critics agreed. Checking the Web sites that monitor reviews, I find that at RottenTomatoes.com the movie scored a 26, at Metacritic.com a 27. Passing grade is 60. The American public effortlessly shrugged off this warning cry and raced to the box office to throw away $54 million. Now here comes a truly inspired animated feature named "Lilo & Stitch." How will it do? It's one of the most charming feature-length cartoons of recent years--funny, sassy, startling, original and with six songs by Elvis. It doesn't get sickeningly sweet at the end, it has as much stuff in it for grown-ups as for kids, and it has a bright offbeat look to it.