I love this song!
It can be about so many people. It is probably not about Michael Jackson because this song was written way before he passed away. It does fit though because mj was the King Of Pop, but his power did wear out too soon.
It also could be about to Elvis (Elvis Presley), who was The King. Not of Pop, just The King. "long live The King" might be reffering to how fans scoured the streets after Presley passed away. Elvis always had almighty power when it came to music, and he was missed quite a lot.
It could be about President of America, Barack Obama, because he is now thought to be the leader of the world (a. K. A. "the king"), but nobody knows if he can handle this much power or if his power will slip away.
It also might be Napoleon. He was very strong and won nearly all of his wars, except of course the Battle of Waterloo when he was finally defeated and put on an island all by himself where he eventually died at the age of 52 of stomach cancer.
But what I reallly think is that the song is about The Crusades, because of "Roman Cavalry".
P. S. Please vote up not down thanks =]