Now that I've seen The Queen, I can say without question it was a better movie than The Departed. No contest. Along with Little Miss Sunshine, that's two more Oscar worthy.
Historical dramas are always interesting from the standpoint that you wonder how much is guessed or exaggerated. Regardless, I thought the guy who played Tony Blair was awesome, as was the Queen.
The British monarchy is fascinating to me. It's such a strange institution, and despite temporarily feeling it wasn't necessary, the Brits seem to really place some value in it again. It's something unique about the country.
Diana was certainly an interesting figure too, and the people who showed up to mourn her death, that was staggering. To have a public figure that inspires people so much... that's something we could all use right now.
I enjoyed all three movies, and would place Little Miss Sunshine at the top of my proverbial list.
I was very surprised with how much I enjoyed The Queen. I agree with your comments about Helen Mirren (Elizabeth) and Michael Sheen (Tony Blair).
It was hard to imagine that Helen Mirren was the female lead in The Cook, the Thief, His Wife & Her Lover (a bizzare little Peter Greenaway flick that defies description). To me this is what makes an actor great. When I see Nick Cage or John Travolta for example, they are just Cage and Travolta (Face//Off reference unintentional). Jack Nicholson, God love him, plays the same guy most every time. But I am hard pressed to think of an actor who can be more than just their seminal character ( Jason Mewes maybe :) )