In studying Shakespeare's Romeo and Juliet, I do not believe that it serves as an archetypal love story. I believe it is archetypical of the "star-crossed lovers" love story.
In terms of Shakespeare and prevalent themes in his plays, change plays an enormous role in providing his plays with in-depth and believable characters, and these changes drive the plot. The protagonists, for example, in Macbeth and Hamlet, go through extensive changes based upon who they are, their journeys of self-discovery, and their interaction with the other characters.
Romeo is a young man, and his experience of life is limited. It would appear that he has never truly been in love, but has been infatuated with Rosaline, another member of the Capulet household. We never meet the object of his affection, but certainly see enough of his immaturity—perhaps a "puppy love"—that has no real substance; but we see a great deal of "suffering" on the part of Romeo. The fact that he transfers his affections so quickly to Juliet may be the clearest, and perhaps the last, indicator of his immature outlook on love, and life.
Once Romeo commits himself to Juliet, every step seems sincere, and the very adult world around him brings clarity where there has been none before. Mercutio, Romeo's close friend, is killed by Tybalt; Romeo kills Tybalt, Juliet's cousin. The casual nature of Romeo's existence, once spent mooning over Rosaline, has altered forever. It could be argued that these things, as well as Juliet's total acceptance of him regardless of his family's name, force him to turn a distinct corner in "growing up." The fact that he takes his own life when he believes Juliet is dead could be an indication of the depth of his dedication, but this is debatable: is it mature to commit suicide in the face of loss?
I personally see no difficulty in perceiving Romeo as an immature young man at the start of the play. However, I do not believe an audience is predisposed to see this as an archetypal love story—there are many doomed romances in Shakespeare's tragedies. Romeo and Juliet are seen as archetypical sweethearts whose fate is predestined—they are doomed before they meet, their ending "written in the stars." (See the Prologue.) There is much discussion, in fact, as to whether the lovers could have done anything to change the outcome of the play.
The archetypical love story, in general, does not, I believe, require death and/or unrequited love. If we look at this love story as archetypical of Shakespearean love in his tragedies, where there are no happy endings, perhaps there is validity to the concept. The Bard's happy endings seem reserved (obviously) for his comedies. However, in general terms, I don't see Romeo and Juliet's tragic relationship as the model for an archetypical love story.