I'm posting late and decided to copy Julia's idea for a post, but no worries, my list is entirely different!
1. Elizabeth I by Margaret George
The most thoroughly researched, well written, original work of literature about the Virgin Queen I have ever read. And that's saying a lot, as I've devoted a lot of time to studying and writing fiction written about Elizabeth I.
2. The Autobiography of Henry VIII by Margaret George
See above, and substitute "Henry VIII" as the subject.
3. The Queen's Fool by Philippa Gregory
4. The Virgin's Lover by Philippa Gregory
5. Gilt by Katherine Longshore
6. The Winter Palace by Eva Stachniak
The first book on the list that isn't Tudor-related, this is a novel set between the reigns of Empress Elisabeth and Catherine the Great of Russia. The most enchanting book I've read in 2012.
7. Elizabeth I by Alison Weir
This is a biography, but if you're truly a Tudor fan, you'll want to read it.
8. The Sister Queens by Sophie Perinot
About the thirteenth century Provencal sisters who became Queens of England and France.
9. Four Queens by Nancy Goldstone
A biography of all four thirteenth century Provencal sisters, Queens of England, France, the Holy Roman Empire, and Sicily.
10. Wolf Hall by Hilary Mantel
Doesn't need me to push it, especially in the wake of the sequel Bring Up the Bodies, but for perspective and especially originality of language rivals George's Elizabeth I.
I also second Julia's recommendation of The Red Tent by Anita Diamant, which really set the standard for historical fiction in the past couple decades.