My favorite romance trope is the "marriage of convenience" story. Seven of my first nine published historical romances followed this trope, including my first published book, A Duke Deceived, which was a finalist for Best First Book (Holt Medallion) and won the Notable New Author distinction back in 1999. My 2005 One Golden Ring (the enhanced version now titled His Golden Ring) won the Holt Medallion as Best Historical, and it too was a marriage-of-convenience story. So I think readers must like marriage-of-convenience stories as much as I.
In my House of Haverstock series the first three of these lighthearted romances are marriage of convenience stories.
Another of my favorite tropes in a romance novel is the "ugly duckling" story. I used this in my To Take This Lord, His Lordship'sVow, and in my novella "Home for Christmas" which appears in my Christmas anthology Christmas Brides: 3 Regency Novellas. I also used it in my novel My Lord Wicked, which won Best Historical in the International Digital Awards in 2011. I think we all love to pull for the underdog, especially the Plain Jane who gets the prince. Those resonate with all us Plain Janes who seem to populate the earth.
Still-another favored trope is the "fish-out-of-water" story. I like, sometimes, to take a nerd who's uninterested in romance and make the sparks fly. I did this in my 2014 Love in the Library (Brides of Bath Book 5) and its sequel, A Christmas in Bath. To me—who's married to a nerd—nerds can be very hot.
What are your favorite tropes in romance fiction?--Cheryl Bolen's last release, Miss Hastings' Excellent London Adventure, used a marriage-of-convenience trope.