I'm jumping on Jessica's bandwagon here, to honor Kathleen Windsor, author of Forever Amber. See link for more details.
This is hard. And they're not in order. I tend to remember authors better than individual titles, so in some cases I've picked the author and then guessed on which book it was that I liked the most. And yeah, I cheated-- they're not all exactly romances, but they all have strong romantic elements. (links go to related Alpha Heroes posts)
1. Gone With The Wind, Margaret Mitchell (duh)
2. Outlander, Diana Gabaldon
3. Mists of Avalon, Marion Zimmer Bradley
4. Kushiel's Dart, Jacqueline Carey
5. Captive Passions, Fern Michaels.
6. Earth Song, Catherine Coulter
7. Through a Dark Mist, Marsha Canham
8. Spymaster's Lady, Joanna Bourne
9. LaVyrle Spencer, either Sweet Memories or Morning Glory
10. Captives of the Night, Loretta Chase
11. Shattered Rainbows, Mary Jo Putney
12. Lover Revealed, JR Ward
13. The Lady Chosen, Stephanie Laurens
14. Timeless Passion, Constance O'Day-Flannery
15. Bet Me, Jennifer Crusie
16. Fancy Pants, Susan Elizabeth Phillips
Hmmm. Maybe in 2010 I'll see if I can actually review all of these. That would be a fun goal.