Not only does the subject matter and the way in which it is dealt with set West Side Story apart from other musicals, on both screen and stage, but the characters in West Side Story are alive, vital and interesting, as well. Despite the fact that not all of the characters survive due to being overly tough and aggressive, they, too, deserve to be mentioned as being interesting, vital and alive in spirit, as well.
From the warring Jets and Sharks and their girls, to the cynical, bigoted and bitter Lt. Schrank and his partner, Ofcr. Krupke, the philosophical Doc, the Candy Store owner who tries to steer the Jets and Sharks in a better direction, to the romancing Tony and Maria, as well as the Shark gang leader, Bernardo and his firebrand of a girlfriend, Anita, all of the characters move about fluidly, freely and expressively, especially when the film version of West Side Story is viewed on a great big, wide movie theatre screen, with the lights down low, and with a whole bunch of other people, whether one knows them or not. Yet, in addition to being a devout fan of the film version of West Side Story, I've seen a number of exciting stage productions of it, as well.
When one sees a movie, especially on a great big, wide movie theatre screen, s/he has to be willing to temporarily suspend any disbelief that they may have. West Side Story, overall, is a musical in which all of the characters are quite believable. Contrary to what many people say and/or think, even Richard Beymer's Tony and Natalie Wood's Maria come off as being far more vital, alive, interesting and believable when this great classic film is viewed on a great big, wide screen, in a real movie theatre, with the lights down low.
Not only does the dancing in West Side Story help provide it with strength and fortitude, but so do the all of the songs, due to their complexity and the way in which they help tell a beautiful story, as well. I have to admit, however, that although I didn't much like the song "Something's Coming'" very much for quite some time, this song, too, grew on me, and I did get to like it. The more I thought (and still think) about the meaning of Something's Coming", the more I realize(d) that this song, too, was not only an integral and vital part of the story behind West Side Story, but that it also has a really true meaning to it; it's a prediction, premonition and an omen of what is to come; Good and bad, pretty much at the same time. The song "Tonight" is also a premonition of what is to come, especially the first two phrases of this song:
"Tonight, tonight, won't be just any night.
Tonight there will be no morning star."
These two phrases are the biggest indication of what this song predicts, as well; Tony's romance with Maria, the sister of the Shark gang leader, Bernardo, and the fact that, due to hatred and conflict between the Jets and Sharks, as well as tribal/ethnic loyalties, Tony and Maria's romance will not see the light of day.
The fact that West Side Story, as a movie/musical, is a combination of so many different events that take place, which, in turn, fuel the various emotions, and therefore the dancing, is also what gives this great movie/musical its strength and enduring fortitude, and makes it as relevant, even today, as it ever was. So many things that went on back then, and still go on, also give West Side Story its strength. Urban gang warfare, racial & ethnic tensions, romances that take place across racial, ethnic, religious and socioeconomic lines, the immigration experience, conflict with the law, substance and alcohol abuse, and tribal/ethnic loyalties that result in protection and honor, and yet often have deleterious results, as well. There are romances across various lines that succeed and flourish, even resulting in dating and intermarriage as well as the raising of families, and yet, some romances/marriages go up in smoke due to tensions, hostilities, and hidebound, insular tribal, ethnic and cultural loyalties.
Sometimes disapproval and hostilities on one or both families or tribes motivates two young people to come together and stay together. Other times, however, this same sort of disapproval and/or hostilities on the part of one or both families or tribes can and will cause romances to dissipate...and to be destroyed altogether. Even though West Side Story is an indication of the latter, it conveys a double-edged sword of a message and teaches an important lesson, despite its being fiction: The deleterious consequences of racial, ethnic and cultural prejudices, and yet it sends a ray of hope, in that intergroup reconciliation, as difficult as it often is, has the possibility to take root and develop. The strength of West Side Story, overall, is such that it delivers such a message.
Some other strengths of West Side Story that have been mentioned on another thread on this board, but bear repeating, is the fact that:
(A) when it was transferred from stage to screen, it was preserved as a larger than life-sized piece of theatre.
(B) Although racism and sexism are fully and openly displayed, West Side Story also speaks loudly and clearly against those two ism's.
(C) While West Side Story is strong on both screen and stage, the cinematography and the costumes of the various characters, as well as the beautiful mixture of colors, and, particularly, many uses of the color red, show the strength of this movie/musical, and also help narrate the story in the film version.
D) The fact that while West Side Story is fiction, it's also based on certain realities.
E) The intensely brilliant Leonard Bernstein musical score, made complicated and interesting by many groups of three notes that sort of jump, very much like the sound of a sofar, or ram's horn.
F) All of the songs from West Side Story aid in the narration of and strengthening of this great movie/musical.
West Side Story is beautiful, strong, and complex, although it's quite easy to understand. As a film and as a stage play, West Side Story, overall, as a musical, is popular due, at least in part, to its strength and vitality, but also to the fact that it's something, that due to its subject matter, the kind of environment that it's set in, the fact that the very story behind West Side Story is also based on certain realities, and, to some degree, does reflect things that go on in real life, despite its being fiction, and the fact that a hint of reconciliation comes as a ray of hope when Riff, Bernardo and Tony, all leaders at some point or other, go down for the final count.
All of the above having been said, I believe that all the above-mentioned factors together give West Side Story its strength, fortitude and timelessness, and bring people to see it, either on screen or stage, even to this day, because its strength is also its relativeness, even today.