"Legs Diamond," the $5 million musical that sold $10 million worth of tickets before it opened at the Mark Hellinger Theater Monday, is a big, beautiful show without the heart that made its precursors - "Pal Joey" and "Guys and Dolls" - memorable stage hits.

"Legs" is strictly a showcase for the considerable talents of Peter Allen, the Australian-born entertainer who has not been seen on Broadway since he appeared in a one-man show in 1979. He and an associate, Charles Suppon, conceived "Legs" in 1984 and they have been working doggedly to get it into presentable shape ever since.When the show opened, it had been playing to preview audiences for nine weeks at the full box office price, $50 tops. It was badmouthed so scathingly by disappointed previewers that two opening dates were postponed and serious revisions made, including elimination of two principal roles and creation of a whole new opening scene.

Still, the word was out - "Legs Diamond" was a lame duck even if it had sold enough tickets to run through February. The truth is, the show has its share of solid entertainment values - terrific David Mitchell sets and Willa Kim costumes, clever staging by Robert Allan Ackerman, and flashy choreography by Alan Johnson.

What it does not have is a meaty book that provides us with characters we care about and a musical score which offers variety and melodies that demand to be remembered.

Since Suppon's original book was totally rewritten by the talented Harvey Fierstein, who should be ashamed of those amateurish double entendres, and Peter Allen is credited with all the merely pleasant music and unimaginative lyrics, the fault must be shared by them. The music probably sounds even better than it is thanks to Michael Starobin's fine orchestrations.

Diamond (1896-1931) was a Broadway hoofer turned gangster who inspired a 1960 Warner Brothers movie, "The Rise and Fall of Legs Diamond," and a 1975 fictionalized biography, "Legs," by William Kennedy. The musical follows Diamond's career from his release from prison to his rise to notoriety as a speakeasy cabaret proprietor involved in a gang war with bootlegger Arnold Rothstein.

Allen gives Diamond very little dazzle, portraying him as an unsympathetic cad who treats an aging girlfriend, Flo (Julie Wilson), unspeakably and uses Rothstein's mistress, Kiki Roberts (Randall Edwards), shamelessly in his climb up the ladder of dubious success. When he is fatally shot atop a mirrored ballroom globe, it seems a case of good riddance rather than a regrettable finale.

Allen is a performer of high voltage energy and agile, somewhat campy grace but he never gets into Legs Diamond's personality deep enough to make him believable. He can deliver a somewhat derivative song such as "Say It Isn't So" with a certain raw style and tap up a tornado in the dance department, but it isn't enough.

His best moment is a cabaret-size song, "All I Wanted Was the Dream," which he begins seated at the piano. More of this sort of thing might have made a difference to "Legs Diamond," a show sadly lacking in intimate moments.

Diamond doesn't carry a gun and Allen doesn't pack the knockout punch necessary to realize the ambition of creating a Broadway musical in the great tradition of the 1940s and 1950s. If he had, then the admirable efforts of the rest of the cast would not have been in vain.

Julie Wilson, a musical actress who has concentrated on supper club appearances in recent years, is a tower of strength as the disillusioned, sharp-tongued Flo, a compulsive good samaritan whenever it comes to helping Diamond out of the rough.

Wilson can convey more with a movement of her heavily lashed eyes than Allen can suggest in a whirlwind flurry of gestures. Her torch song, "The Music Went Out of My Life," although inserted into the sagging second act in a way that slows its already slacking speed, is the most touching moment and best music in the show.

Randall Edwards' role is inspired by Adelaide, the dumb blonde in "Guys and Dolls," and she plays it to the hilt and beyond.