Interesting question. I have always thought that it is hard to acurately state what the most "important" means. I suppose that is has much to do with what would have happened if things would have gone otherwise for the Anglo-Saxons. It is dangerous to conject into the future, and the whole "what if" game can gain one bad practices. But if that is the criteria, Brunanburh may have to be the second most important. If Edward and his brother would have lost the battle, then the northern kings would have enjoyed a stable frontier, at least for awhile.

I hate to be cliche, but next to Hastings, Stamford Brisge and Fulford gate may be the next most important battles in Anglo-Saxon England. If Morcar and Edwin's forces hadn't been smashed by Hardradda, then the forces at Stamnford and consequently, Hastings, would have been larger. People can argue with me on that one, but I'm set on it. And then obviously, if Stamford wouldn't have been fought, there would have been much larger numbers to fight Duke William with. It's all conjecture, but some of it is very important.