(Gerard Depardieu and Jack Lemmon, as Reynaldo and Marcellus respectively, are here only briefly and look understandably adrift.) Blink and you'll miss John Gielgud, who has no dialogue as Priam in a flashback role. Some of the star turns are here for blatant marquee value and stand out as gratuitous. Alex Thomson's cinematography captures this swank atmosphere in all its gilt-edged glory. In between, the film's many stars parade in velvet and braid through ornate chambers that are built on a cathedral scale. There are torrents of confetti when Gertrude weds Claudius, and a final fencing match on a scale that Rocky might envy. Sometimes resorting freely to unlikely touches, this film has earthquake special effects and a horror-film look when its ghost arrives. He makes a dashing figure if not a terribly melancholy Dane, typifying this film's preference for bold strokes over gloomy introspection. Branagh remains a great popularizer of Shakespeare and now has the chance to speak some of the most famous lines in the English language as if they had just come to mind. His own performance is the best evidence of all. Branagh's version of ''Much Ado About Nothing,'' takes a frank, try-anything approach to sustaining its entertainment value, but its gambits are most often evidence of Mr. Branagh holds court throughout a four-hour, 70-millimeter sumptuously appointed production that doesn't often lag. Heading a cast so stellar that majestic Blenheim Palace plays the role of Elsinore, Mr. Kenneth Branagh's fine, robust performance as Hamlet is the bright centerpiece of his lavish new version of the play.