Given the fact that this is a B movie the rating automatically goes to, say a 2 or less on the big budget scale. So, given that it will be a 1 or a 2 to begin with, if you have to break that out from 1 to 5, I would give it a 3.5.
Why so high, and why would I rate it higher than the D&D movie?
The dragons were done right, except for the fact that they were from space. They could have come up with something better than that. I suppose they were trying to answer the question of why dragons weren't everywhere if they were native to Earth. Still, they could have done better than that. Notice that they leave the door open to a sequel by showing another dragon egg hurtling towards Earth. I actually predicted that before they showed it. Very formulaic for a B movie.
JRD definitely gave a better performance than the rest of the cast, but I suppose that is to be expected. Heck, he was better than Jeremy Irons in D&D. I would say the ranger gave the worst performance. He was a likable enough guy and he played the rebel well enough, but as has been pointed out already, he did not know how to hold a bow and the way he delivered his lines was just awful.
I enjoyed the monk and the wizard (yes, he was a wizard, he just couldn't cast spells). They were fun enough characters. Other than the wizard I had no problems predicting who would die. This movie had a serious case of red shirt syndrome.
I liked how they brought the movie to a climax with a fight to restore the proper king to the throne while dealing with the dragon.
In other words, it delivered what it said it would deliver for a B movie. I certainly have no desire to sit through it again, but it was fun enough while it lasted. If only every movie with a dragon in it could do them the justice that this one did.