That is, is there a set of titles every true romance-novel fan has read (or will never admit otherwise)?
I don’t know the answer to your question, but I’d suggest you change the thread title, or you’re going to get a lot of smarmy responses!
I don’t know about specific works, but there are specific authors whom I’d consider key to any kind of canon for romance fiction:
Jane Austen (usually Sense and Sensibility and Pride and Prejudice)
Georgette Heyer
Dorothy Sayers (Her Lord Peter Wimsey books, from Strong Poison onwards, particularly from Gaudy Night on.)
I’m sure there are others that would be considered influential and generally read. These are simply the three that I believe are most influential for the sort of romance I read.
Just like when you ask someone in any genre to name what they consider to be the canon for that genre, there’s going to be plenty of variation in those lists, too.
Wuthering Heights?
I Hadn’t thought of that until you mentioned it. 
yes, there is, Brianglutton.
/me loads powder into Romance canon
/me loads Brainglutton into Romance canon
/me lights the fuse to Romance canon and watches him soar into the distance when it fires.
“It’s a Brainglutton broadside for the romance ladies’ backsides!” I shout, then smile at the thought of a job well done.
The gals over at SmartBitchesTrashyBooks addressed this very question in a recent podcast.
I suppose ***Wuthering Heights ***would have to be in any such canon, wouldn’t it?
Are we limited to novels, or are poetry, theater and film included?
I was thinking novels only – by “romance-novel fan” I mean the kind who shops in that section of the bookstore.
I got yer romance cannon right here! [grabs crotch]
In that case, there are surely canonical authors (Judith Krantz, Danielle Steel, Barbara Cartland), but no canonical titles.
If we’re talking “category romances” (the sort of thing you see for sale at the grocery store, e.g. Harlequins), they typically do not remain in print for long. It’s my impression that both the publishers and the fans treat these novels like magazines. They’re available for a short period, fans buy new volumes regularly and read them once or twice, and then they’re discarded or stashed away. There doesn’t seem to be much interest in old category romances – they get donated in large numbers to library book sales and charity shops, but it’s not easy to resell them. I’ve seen them go for a buck or two per bag.
Throw in the Brontes (including Jane Eyre) and Rebecca, and I think you’ve pretty much got it.
Oh yes, there is such a thing and “romance cannon” is one of its many pet names, ladies.