The Broadway program for “Hair” did not look promising.

First, a turn-off-your-cell-phone insert offered inane urgings to “turn on” my eyes, my ears, my skin. Then, I turned to the cast biographies to find that grown-up actors had replaced their professional credits with hippy-dippy goo-goo talk about their astrological signs and their love for peace and cats and karma and, you know, man, their love for love.

And I’m thinking uh-oh.

It appeared the worst had happened. “Hair,” which the Public Theater first resurrected for three unpatronizing and purifying performances two summers ago and for a fully staged one last summer, had finally been inflated into a ‘60s theme park for Broadway.

In fact, “Hair,” which opened March 31, turned out to be a terrific and important revival. Despite the icky program notes and a tendency to sell too hard, the Public Theater’s production passionately trusts the material about Vietnam protests, sex, drugs, civil rights and other liberations from the passive veneer of post-World War II America. Under Diane Paulus’ steady direction, the show takes its context seriously enough to find its own style.

But my pre-curtain dismay gave me an epiphany about nostalgia. Was I feeling nostalgic for last summer’s production or for the simpler one the previous summer? Or was I thinking that, 42 years after the original, all authentic impulses from the turbulent ‘60s had been squashed forever as naivete and fashion statement?

I am also having a more anxious thought. After a while, are all regular theatergoers destined to become like those old soldiers who grumble, to anyone who’ll still listen: “Ha! You think D-Day was a big battle? You should have seen Appomattox!”

Comparisons may be odious. But with so many revivals these days, comparisons are getting impossible to avoid. Not so long ago, much of New York theater - on Broadway and off - was new. Every season had just a handful of revivals, including whatever you want to consider Shakespeare and the rare showcase Greek tragedy.

But look at the heft of yesterday’s musicals today. Since December, Broadway has brought back “Pal Joey” (1940), “Guys and Dolls” (1950), “West Side Story” (1957) and “Hair” (1967).

In all of them, I hoped for the sort of living connection to the past that electrifies the Lincoln Center Theater’s magnificent revival of “South Pacific” (1949). How surprising that “Hair” - presumably the most dated - comes closest to that exhilarating level of trust in audiences and in the original.

The biggest disappointment must be “Guys and Dolls,” which, despite negative reviews, is doing big box office. Director Des McAnuff seems not to have believed that these beloved Damon Runyon characters and their witty, ravishing songs could have been spoken today without being tarted up with dizzying scenery, ugly-edged choreography and updated musical arrangements. There is something wrong when the actors, including stage newcomers Lauren Graham and a miscast Oliver Platt, get so lost in the scenery.

And could Arthur Laurents - original author and director of the current “West Side Story” - have been so consumed with his drive for a mean-street bilingual revival that he overlooked the basics? The casting, except for Josefina Scaglione’s Maria and Karen Olivo’s Anita, is shockingly bland, and the physical production is cheap in imagination if not in budget. Still, there are those glorious songs, that story, the dancing. Really, that’s good enough.

“Pal Joey” always had a weak book that kept it from being revived more often. We had major hopes for director Joe Mantello’s rethinking, but a low-wattage production and dull casting in the starring role removed any chance that co-stars Martha Plimpton and Stockard Channing could galvanize the sophisticated show.

The past also haunts and challenges a boom in play revivals. Blame the economy, the power of branding or - to put a happier face on it - a desire for a new generation to experience the theater’s pre-existing conditions. By the time the Broadway season ends April 30, we will have seen revivals (predominantly star-driven) of “Hedda Gabler,” “The Seagull,” “All My Sons,” “Speed-the-Plow,” “American Buffalo,” “Exit the King,” “Blithe Spirit,” “Joe Turner’s Come and Gone,” “Mary Stuart,” “The Norman Conquests,” “The Philanthropists,” “Desire Under the Elms” and “Waiting for Godot.”

Such repertory - old and fairly recent - can be deeply gratifying. But I miss the time when more producers wanted to be linked to world premieres, or at least transfers of new work from London and around the country. Unlike classical music, which basically presents the same 50 masterworks in different interpretations, theater constantly confronted us with new ideas. It was a messier process than evaluating an opera or a symphony. We had far less guarantee of great art, but more opportunity for genuine discovery.

I just learned that nostalgia comes from nostos, which is Greek for returning home, and algia, meaning “pain, grief, distress.” We’re told we can’t go home again. But the best revivals, the ones that understand why shows survive, seduce us to filter our memories through someone else’s idea of home.