So here they are in alphabetical order:
Mary Balogh
She was the first romance novelist I read, and her first book I read, Slightly Dangerous, is still one of my favorites. In fact, I bought it, which is unusual. She writes historical fiction about Regency England. The really great thing about her stories is how much you care about the people. The books always start out sort of frothy, but have much more depth as you go along, with the characters becoming more and more complex. There are some of her scenes that I like to read over and over either because they are so much fun or because they are so satisfying. She has several series that are all distantly connected, meaning the author often uses a main character from one book peripherally in another -- a familiar and beloved face.
Catherine Coulter
She is a prolific writer with several different series, from modern thrillers to historical fiction, but the only ones I've read are the Viking series: Lord of Hawkfell Island, Lord of Raven's Peak, and Lord of Falcon Ridge. I think these are more historical and adventure than romance, but whatever, they are fun to read.
Jude Deveraux
Another writer with several series. Mostly I've read her modern-day novels about Edilean, a small town in Virginia close to Williamsburg. There are a bunch of those. But my very favorite of hers is Wild Orchid. It has a supernatural, or fantasy aspect to it but very modern at the same time.
Diana Gabaldon
She has a series of very long books about one family in Scotland. The series begins with Outlander, which is my favorite. It's about a nurse just after World War II who accidentally goes back in time (I'm a sucker for time-travel stories) to Scotland around the time of the Uprising. As much as I liked the book as a whole, I did not like the ending, which was a shame after putting in so much time with this very long book. But I'll let you reserve judgement.
Amanda Quick
This author goes by at least three names: Amanda Quick - Jayne Ann Krentz - Jayne Castle. The Krentz books are modern romances while the Quick books are historical romances, set in either Regency England or Victorian England. Some of them are also slightly supernatural. Although the Krentz books are good, I like the Quick books the best. In fact, one of hers called Scandal I liked so much that I did something I've never done before. The minute I finished it, I started over at the beginning and read it all through again. I've never read any of her Castle books but I understand they are "futuristic/ paranormal romantic - suspense writing."
And those are my current favorites. I did not mention the most famous ones like Nora Roberts or Danielle Steele since everybody knows about them; and although they're okay, they're not as good as some of these others -- in my opinion.