How about you run to an area where he can't fly and use some good old tactics? Or why don't you pick up a bow and start shooting away... Hmmmm no?
Ok learn some arcane and start blasting him with magical bolts of sit down.
Honestly though I think Skyrim is going to be such a diffrent game (better) that when it comes out and we compare it with past TES games it's pretty much going to be on a whole nother level. I mean they have a new ENGINE this should tell you alot right there.. Multiple dragons on 1 screen?? That right there says We can probably see small armies of NPCs going against each other.