I think a point and click adventure mini-game would be suited to dragon slaying.
You have a set amount of time (depending on your and the dragons levels) and you must find the items required to slay the dragon. Different dragons will require different items. For instance, an ice dragon will be beaten with fire, so you need to find the unlit candle. But you also need to find the matches to light the candle. If the dragon breathes fire, all you need is water based items.
Both will require a delivery system. This will be common to all dragon mini-games. I figure a glass-tipped arrow (the glass from an alembic) filled with the dragons counter element can be fired from a bow. Then a cutscene plays if you beat the timer. If you don't beat the time, you have a second chance (only 10 seconds) to beat it. If you beat it in this second chance time frame, the quest you're on will be altered in a negative way (lower gold reward, less experience etc.).
That is how dragons should be dealt with.
Lol seriously?
This is/was a challenge to the developers I'm sure(if it wasn't they didn't do it right) If I was doing it I would have them fight both in the air and on the ground. While in the air they would swoop down from a random direction and basically try to tackle you then go up into the air, while you could be: shooting arrows or spells at it, or waiting patiently for the dragon to swoop down and make a pass while you carefully dodge and slice/whack at it while it zooms past you. It would also shoot fireballs at you from time to time(not ones that hit the ground and disappear, like spells from past games, but ones that hit the ground and start a small fire that stays lit for at least a few seconds) After it gets tired of flying/swooping it will land and with the fury of 10000 deprived skooma addicts throw its arsenal of attacks at you(claw, bite, fire, etc) If you take too long it will get impatient and fly up and and repeat the steps.
That sounds pretty dynamic imo and a fairly easy concept, that would probably be the easiest of possible dynamic solutions.