I know we've done it for Pumpkin Ales. Luckily, Christmas beers seem to have a much greater selection than Pumpkin Ales, probably because it's a more standard, traditional category. I find very few that outright suck.
Troeg's Mad Elf is probably my favorite. Then there's a whole collection of local ones that taste pretty similarly: Great Lakes Christmas Ale, Thirsty Dog 12 Dogs of Christmas, Fat Heads Holly Jolly Christmas Ale, Southern Tier 2XMas. The Breckenridge is very good and even though it's not a traditional winter warmer, the Great Divide Hibernation Ale is one of my favorites.
I don't think I can even get into the Belgians, but there's a lot of them too. I think the Scaldis Noel is probably my favorite, but I haven't tried many.