After a few moments of hard staring, I found that I agreed: not because comparing the writing quality of a Young Adult swords & sorcery epic trilogy to the Bard was a sane proposition, but because Romeo and Juliet are not a romantic couple. Yes, Mae's shirt did help. :D
I have reproduced my natterings herein, complete with a reworking of the first 10 lines of III.V with some slightly more modern references.
Clary and Jace are a way better relationship because Romeo and Juliet are a great tragic couple, not a great romantic couple. Romeo and Juliet are together pretty much from the start, and we know it's going to end badly.
If both Romeo and Juliet had lived, if communications hadn't been crossed and Romeo had gotten the message and hadn't killed himself, what would have happened to them? They basically ran off and had the equivalent of a Vegas wedding, way underage by today's standards. Their relationship was based on:
* Romeo seeing the hot chick across the room while he's on the rebound
* A conversation where they have no idea who the other one is
* Him hollering up at her window
* Secret wedding
* Steamy night of passion
* Juliet's father's attempt to shove Juliet at Paris two years earlier than he'd been thinking about having her get married
Juliet isn't even 14. If they'd survived, they would have gotten to know each other better, and any character flaws would have had time to emerge. Not a week before he married Juliet, Romeo was head over heels for some girl named Rosaline. Who's to say he would have stayed faithful to Juliet? He might have realized a month later that Juliet was not the girl for him, and gone after some other woman. Juliet might have turned clingy and controlling and manipulative and always trying to get her own way.
J: Why are you up? It is not yet near day.
It was a car alarm, and not the clock
That stirred you from your well-deservèd rest.
Nightly its wails disrupt our slumbers
Believe me, love, it was the car alarm. 5
R: It was the clock, Aeon's vile minion,
No car alarm. Look, love, what rusty streaks
Corrode the well-primed clouds in yonder East.
The streetlamps have switched off, and cruelest Sol
Begins to fade the tinted mountain-tops. 10
True, they might have stayed married because divorce wouldn't be legal for another 60 years, and Juliet was a year too old for an easy annulment (according to the cursory research I did), but nothing in the situation setting them up guarantees them a happily-ever-after.
They are, instead, tragic. They are *star-crossed* lovers. The whole world, the very heavens, are conspiring against them.
They start out from warring families, they see each other without anyone warning them off that no, that hot chick is actually currently in that little feud you have going there, and they're both teenage enough that the person you're madly in love with is the person you will love forever and ever amen (even if you changed your mind last week about that). They manage to bully the adults around them into allowing the local equivalent of a barely-legal Vegas wedding, and no one has the sense to stop them. A *secret* wedding, that four people total know about.
Romeo then gets into a street brawl, gets one of his best friends killed, and slays his cousin-by-marriage, and gets kicked out of town. At no point does he mention anything like his secret wife. Juliet's father decides that this is the perfect time to step up the timetable on Juliet marrying Paris. Juliet's nurse isn't so good at reading the danger signs in star-crossed teenagers, for all she's known Juliet since she was born, and fails to either talk sense into Juliet or to alert anyone else that there's something wrong with this picture, and the parents aren't having any listening either.
Juliet says she's going to kill herself unless the loon who married them has some better idea, and he hatches a cracked plan that's at least a little better than her killing herself, but not much saner. Romeo gets the wrong message, and comes back before Juliet is conscious again, and kills himself minutes before she wakes up. The friar shows up too late to catch Romeo, just as Juliet is waking, but buggers out of there for fear of being caught, leaving Juliet alone with the dead men. (Yes, leaving a girl who was suicidal the last time you saw her alone within reach of a weapon in the presence of her dead husband is a *great* idea.) This leaves her free to kill herself, which she does.
In contrast, Jace and Clary have plenty of time to get to know each other, and now that the confusion about Jace's parentage has been cleared up and they're no longer in an active war zone, their relationship has a fighting chance. They've overcome enormous obstacles to be together, which is a sign of a romantic couple.