We should never forget Trogdor, the Burninator.
Shadow of the Colossus has some of the best dragons I have seen in video games (okay, technically, they're colossi). That game is simply stunning in the way that it portrays the size and power of the huge beasts. The worst portrayal of Dragons in video games is Lair for the PS3, which is one of the most disapointing games ever.
Todd McFarlane has a series of dragon toys out that are quite impressing for the price. I am also a big fan of the Collosal Red Dragon mini from DDM, although I think that calling it a "mini" is a bit of a stretch.