SOME PLAYS WE like. Others we dislike. The wooing has been successful or it hasn't. Maybe we can't articulate all the reasons why, but the reaction is firm. It has gathered shape over the evening--easily, naturally, intuitively--and we leave the playhouse knowing just where we stand.

There is, however, a third category of plays, and more often than not, much of our theatrical fare falls within its boundaries. These are the plays we want to like. Secretly we're rooting for them all evening long, just waiting for the moment when we can pledge our full allegiance. "Soon," says a murmur in our hearts or a whisper in our heads, "I will be won over, converted, taken in." But for all the encouragement provided along the way, conversion never quite comes. These plays pull up short just before the finish line, a few strides away from the full headiness of triumph.

Too much has been accomplished to shrug them off as misspent evenings. They've honored some, if not all, of their promises. Expectation has been kept alive for several hours. And yet the final miracle has failed to happen. "Nine" and " 'Master Harold' . . . and the boys," two late-season entries in a Broadway season conspicuously lacking in quality, belong in this sticky category. Both are being touted as all-out hits, probably because Broadway is notoriously incapable of supporting less. Both are unquestionably worthy endeavors. Both also leave us hat in hand, when we wanted to do nothing more than pitch it in the air.

"Nine," a musical version of Fellini's film "8 1/2," at the 46th Street Theatre, is boldly innovative and intoxicatingly stylish, and if only for the risks it takes, it deserved its Tony award for best musical of the year over that cold exhibition of stage machinery that is "Dreamgirls." It unfolds in a white-tiled bathhouse in Venice, a spare, surrealistic locale that actually represents the mind and memory of one Guido Contini (Raul Julia). A celebrated Italian movie director, who has lately run up a string of flops, Guido is careening toward his 40th birthday, bereft of ideas for the new film he's contracted to make in three days.

In addition, he's trying to juggle an elegant wife, an impetuous mistress, and the pristine young actress who once provided the very inspiration that is now failing him. His sharp Parisian producer is breathing down his back. His mother is clucking in the background. And ghosts out of his boyhood--severe nuns and opulent whores, crystalline churchbells ringing out in the candlelit night and hot tarantellas danced on the beach--are coming back to tease and taunt him.

As an exploration of Guido's muddled head, "Nine" is a knockout. Tommy Tune's staging is a veritable act of psychoanalysis, conducted with the flair of a Ziegfeld. Black and white are the dominating colors, and with the exception of his youthful alter ego and three schoolmates, Guido is surrounded entirely by women--statuesque, pure, aristocratic, voluptuous, giddy, grotesque --all of them stunningly played. Insinuatingly melodic, Maury Yeston's score snakes its way like fine smoke in and out of the crannies of this lavish mindscape.

So why, with such riches at its disposal, does "Nine" fail to come up with the big payoff? The answer, I suspect, lies with Guido. Having watched him sink deeper and deeper, "Nine" really doesn't chart a way out of the tangle. Just when his professional and personal relationships come crashing down, a voice from the past--Guido himself, as a tot--sings "Getting Tall." The number presumably represents a turning point in Guido's self-awareness. But its thrust--that we have to learn to make choices in life; we can't have everything and everyone--is just too simple-minded to be satisfactory.

Broadway musicals usually demand the last-minute redemption of their heroes, but Guido, despite the considerable charm of Julia's performance, may be a scoundrel born. His ravenous appetites are irreconcilable. In life, as in art, he is a modern-day cannibal. "Nine" really doesn't know what to do with him, once it has painted him into a colorful corner. Merely telling him to "Grow up" and then packing him off to his faithful wife with a vaguely hangdog look on his face is no resolution at all. It's an arbitrary cessation of the brilliant tumult that presumably seduced "Nine's" creators in the first place.

" 'Master Harold' . . . and the boys" (at the Lyceum Theatre) remains far truer to its material, taking it to its logical and bitter end. As he has in countless plays past, South African dramatist Athol Fugard is digging beneath the surface of apartheid and discovering its frighteningly human origins. Sam and Willie (Zales Moake and Danny Glover) are two black menials in a tearoom in wet and windy Port Elizabeth. Between chores, Sam coaches Willie for the big ballroom contest, two weeks away, and as Fugard's play evolves that contest becomes a symbol for an ideal world "where accidents don't happen" and the participants glide across the floor in grace and harmony.

The moral collision, however, is very much part of Fugard's dramatic world. This time, it will be triggered by Hally (Lonny Price), the bright, nervous white youth whose parents own the tearoom. Hally lives in terror and fear of his crippled alcoholic father, now hospitalized, and has always come to Sam and Willie, as he has this day, for solace and comradeship. In slightly under two unbroken hours, Fugard shows us how the feelings of frustration and impotence Hally nurtures towards his father can be transferred in a foolish outburst of blind rage to the two black men he loves most.

"Master Harold," in short, is pinpointing that awful moment in a youth's life when racisim takes root in his soul and the spittle of hatred stains his mouth. Fugard, however, never talks in grandiose terms. His indicting dramas are built of the humble particulars of daily life in South Africa, and "Master Harold" meanders through an afternoon, devoted to scrubbing the floor and shooting the breeze. But periodically, the telephone on the lunch counter rings. It's Hally's mother and father, calling from the hospital, and each ring cuts, as keenly as a knife, into the tenuous climate of brotherhood in the tearoom.

This is significant material of a kind Broadway rarely sees and the New York critics have hailed it in wildly appreciative terms. The production, directed by the author himself, is considerably less powerful than the play, however, and one suspects much of the praise has to do with good intentions. With an insidiousness endemic to Broadway, "Master Harold" has acquired the dimensions of an Important Event, and that sense of importance has denatured the drama. Price just may not have the skill to illuminate the twisted logic inside poor Hally's confused head, but Mokae, an accomplished actor, nearly undoes a warm and good-natured characterization in the final moments with a tribal keening that could have been borrowed from Zoe Caldwell's Medea. Only Glover, sticking to the bafflement and hurt born of the moment, has the sort of straightforward emotional honesty that serves Fugard best. The actors need to tell us only what happened in that sorry tearoom in 1950. By trying to underline conclusions, this production spends itself in useless labor.

Sometimes, we find ourselves wanting to like a play, simply because an appealing performer has lured us beyond the confines of a script. That was certainly the case of Christopher Durang's "Beyond Therapy," a zany comedy about the troubled waters engendered by the sexual revolution and further muddied by the not-so-artful practice of psychiatry. All too slight and ramshackle to last on Broadway, it folded earlier this month after a brief, but whacky run. But long-time Arena actress Diane Weist happened to turn up in it, as a beguilingly contemporary young woman, caught between a weepy bisexual, who can't quite break with his male lover, and a male chauvinist shrink, who won't let her break off therapy. Weist's performance was by turns so sweetly bewildered and sexily assertive that I desperately wanted Durang's comedy to soar, rather than just flap its wings anarchically.

Perhaps if Broadway didn't promote its wares with such a vengeance, pumping up interesting musicals into once-in-a-lifetime hits, promoting plays of real, if limited merit as unbounded treasure troves, we could be more philosophical about matters. A play we want to like more than we actually do has not really failed. Basically, we're on its side. We're admiring, where admiration is due, and once the curtain falls, we have none of the hard feelings, spawned by a flop. The balance sheet is positive on the whole.

In the cockeyed hit-or-miss world of Broadway, however, there's no immediate rush to the show that is less than sensational. So Broadway sells each one as a smash. Urgency is the byword, not honest appraisal, and the hard-sell escalates with each passing production.

What such tactics overlook is that we'd probably enjoy "Nine" and "Master Harold" more if we went in expecting less.

And Weist? Let's pray she's back before long in a play we not only want to like, but can wholeheartedly.