Well, they're certainly attracted by each others' appearance, that much is certain. Romeo literally can't quit staring when he sees Juliet across the room. All thoughts of Rosaline, the girl he was pining and moping and weeping for just hours before, have vanished. Juliet is equally mesmerized once Romeo captures her attention.
I'm not discounting that what these teenagers experience may have been love, and madelynfair makes a great case for just such a thing. My position is that these are impulsive young people, which suggests their feelings may or may not have been love.
First, it is noteworthy that Romeo assumed he was in love with someone else mere hours before meeting his future wife. And Juliet tells her parents only hours before she meets Romeo that she has not even thought about marriage ("it is an honor that I think not of"). Hours later, they're planning a wedding.
Their second impulsive act is to marry--without their parents' knowledge or permission and within hours of meeting one another. They proceed to keep their marriage a secret, each living in their parental homes which is not an ideal scenario but a consequence of their impulsive behavior. They can't even find a way to live together in the same house.
After things go bad (and by bad I mean after Romeo impulsively kills his wife's cousin) and Romeo is banished, their impulsivity soars to new--and deadly--heights. Juliet runs to the Friar and readily accepts his rather risky plan. She will fake her own death and wait for Romeo. Romeo, of course, doesn't get the message in time and impulsively drinks the poison he has impulsively purchased. When Juliet awakes to find her husband dead (he's still warm, even), she impulsively forces a dagger through her heart.
The "romantics" in my class each year are offended that I would call Romeo and Juliet's love into question; however, my case is simple. What these young lovers (for they were that, at least) shared may or may not have been love. Their behaviors were so rash, unplanned, and impetuous, it's difficult to know if it was love, teenage impulsiveness, or both.
This question is an evaluative one, meaning, you must identify criteria for "authentic love." This love contrasts with physical love rooted in desire and admiration of beauty. So, first ask yourself, "What is authentic love? How do we define it?" Now you must look to see if there is any authentic love in the play. You must do the same with physical love, asking yourself, What are the signs of someone being motivated only by desire for physical beauty?
Is authentic romantic love respectful? Is it patient? Kind? Devoted? Is there sacrifice? Identify at least three criteria that you believe are a fair standard for judging the romantic love between two people. I would recommend that you discuss this idea of true and authentic love with someone whose opinions you respect before finalizing your list.
Let's look at Act 1, scene five -- Romeo and Juliet's first encounter. Romeo says:
Look up profane, unworthiest, shrine, pilgrims, and see what connotations these words have in common. In short, these words are all pointing to religious imagery, where Romeo plays the role of a pilgrim at a shrine, which was common in Shakespeare's era. A religious devotee would approach the statue of a saint or the Virgin Mary and pray for intercession on a need that the supplicant had. So, if you had lost a valuable item, you might go to your local church and pray to Saint Anthony's statue for help locating it; if you were in great grief and fear and needed protection, you might go and pray to another saint. So, Romeo is treating Juliet like a holy image in a shrine, acting as a pilgrim there to worship. (Catholic traditions were still alive.) Remember: still look these words up, because they are evidence for your argument. Now ask yourself: do Romeo's first words in his first encounter (essentially, his pick-up lines!) meet the criteria you've established for romantic love?
Examine their entire exchange through the lens of the "authentic love" criteria. How many words do Romeo and Juliet use that have suggestions of respectful, kind, sacrificing love?
Then you want to use the criteria for physical love, or lust, to examine this exchange between Romeo and Juliet. Do you see any signs of physical attraction? Of interest only in the body or physical beauty? You'll note that Romeo takes a physical action and Juliet invites him to do so again. Romeo changes his language, keeping the religious metaphors alive, but this time, it is "sin."
Note that their entire exchange is a sonnet -- 14 lines of love poetry, rhyming, in synch with one another. That's pretty romantic. Is Shakespeare elevating this moment between them to something highly romantic and spiritual?
Is it possible that Romeo and Juliet are motivated by both true love mixed with physical attraction? Could the answer be "both"?
To do a really thorough assessment, look at every scene where Romeo and Juliet are together (especially their balcony scene conversation -- Act 2, scene 2 -- and Act 3, scene 5), and ask where you see the authentic behaviors. Weigh those against behaviors that are more physically motivated.