There’s a reason “The Phantom of the Opera” is the longest-running Broadway musical of all time: It’s THAT good.

With a sumptuous score, a torrid tale of unrequited love, a dark and dangerous mask-wearing villain and a chandelier that nearly upstages the entire lot, “Phantom” remains one of the most lavish and darkly romantic musicals on the boards. (Could “The Music of the Night” be any more sensual?)

So why mess with success?

But that’s precisely what Andrew Lloyd Webber has done with “Love Never Dies,” his pseudo-sequel to “Phantom,” which opened Thursday night at the Cadillac Palace Theatre. It is, alas, a disappointing world apart from the original on almost every level.

‘LOVE NEVER DIES’
Somewhat recommended
When: Through March 4
Where: Cadillac Palace Theatre, 151 W. Randolph
Tickets: $35-$100
Info: broadwayinchicago.com
Run time: 2 hours and 25 minutes, with one intermission

Gone is the glorious score, though there are “Love” songs that are pleasing enough. Gone, too, is a truly meaningful story line, a plot that makes you care deeply about the characters you thought you knew. Where are the tormented souls? The anguish of a love that can never be? Where is the heart and soul in this tepid followup?

“Love” picks up 10 years after “Phantom” left off. Our masked impresario (played by opera veteran Gardar Thor Cortes) finds himself at New York’s rough-and-tumble Coney Island of the early 1900s, having fled France (remember, he killed people in the original musical, though that seems to have escaped the minds of everyone in “Love”) with the help of the eternally frowning ballet mistress Madame Giry (Chicago’s Karen Mason) and her daughter Meg (Mary Michael Patterson, in one the show’s best performances), who are now in his employ at his Mister Y’s (get it?) Phantasma.

Meg, who dances and sings her heart out in whimsical vaudevillian-style vignettes, is in love with the Phantom. But he still pines for his beloved Christine Daae (the stunning and clarion-voiced soprano Meghan Picerno), the toast of the European opera world whom we soon learn is headed across the pond as well, to make her American debut at a new Manhattan opera house.

But upon her arrival in New York, the itinerary is soon sidelined by the Phantom, as Christine and her husband, the dashing Raoul (Sean Thompson), who is now an alcoholic cad who has gambled away his fortune, and their adorable son Gustave (Chicago’s angelic-voiced Casey Lyons,) are whisked away to the Phantom’s theater, where the plot thickens and quickly collapses.

Commanded by the Phantom to sing one last composition of his own or suffer the death of her son, what’s a girl to do? In this case, she soon falls into his arms for a passionate kiss.

Of course, if you’ve not seen the original (or Googled the show’s plot), you won’t have a clue who any of these characters are. And with a sound system that muffles much of the song lyrics and dialogue throughout “Love,” you won’t understand their current incarnations, either.

Meg Giry (Mary Michael Patterson, top) and the ensemble of “Love Never Dies.” | Joan Marcus

With previous stagings including Australia, Germany and London, “Love,” which debuted in 2010, has yet to make it to Broadway — and that’s saying a lot.

And despite music by Lloyd Webber and lyrics by Glenn Slater and Charles Hart, as well as numerous tweaks to the script, the book still fails to capture the magic of the original, let alone find its own solid footing.

There is no “Music of the Night” or “All I Ask of You” or even a pulsating “Phantom’s Theme” to sweep you away, though Webber has occasionally and cleverly peppered the sequel with snippets of the score from the original (sighs of elation erupted from the opening-night audience each time).

The best parts of “Love” are its visuals — the marvelous and eye-popping costumes and massive set pieces by Gabriela Tylesova and the magical lighting by Nick Schlieper — which take your breath away. The glittering sideshow parade near the musical’s onset is a feast of sight and sound on every level, from the garish to the beautiful and everything in between.

The ensemble also is exceptional — particularly Katrina Kemp, Stephen Petrovich and Richard Coons as a trio of carnival “emcees” who pop in and out of the story line.

I have seen “Phantom” nearly a dozen times over the years, in various cities and in several national tours. It has never disappointed.

It remains one of my favorite musicals of all time because the music, the story and, most of all, the characters, are unforgettable. They touch your soul on some level. And isn’t that truly the measure of any great stage production, musical or otherwise?

Young Gustave (Casey Lyons) is intrigued by the mysterious Phantom (Gardar Thor Cortes) in “Love Never Dies.” | Joan Marcus