The first novel that leaps to mind is 'Jane Eyre'. Its influence is so pervasive it's hard to imagine the modern romance genre without it. That journey from the lonely governess to a fiercely independent woman who demands spiritual equality is just stunning. It’s not a simple love story; the Gothic atmosphere and the deep moral wrestling make it so much more.
I'd pair it with 'Wuthering Heights', though I hesitate to call it a romance in a conventional sense. The love between Heathcliff and Catherine is destructive and obsessive, a force of nature that obliterates everything else. It’s fascinating, but not exactly swoon-worthy. For a more traditional, socially-conscious romance, Elizabeth Gaskell's 'North and South' is perfect—watching Margaret Hale and Mr. Thornton clash over class and principle before finding respect is incredibly satisfying.
If you can handle a slower, denser read, George Eliot's 'Middlemarch' offers several profound romantic and marital plots, especially Dorothea's. It’s less about the 'will they, won’t they' and more about the 'what happens after they do,' which feels strikingly modern.