* Dragonslayer is the latest entry in the sword-and-sorcery sweepstakes. Following on the heels of "Excalibur," it's a less ambitious movie; yet -- within its limits -- a more successful one, if only because it isn't so overstuffed with images and obsessions. There's just one dragon, and all the action is aimed at getting her -- out of the way, with occasional pauses for romance between the young warrior and his attractive henchperson. True, there's not an original bone in the entire picture: The hero is straight from "Star Wars ," and the plot is a steal from King Arthur, complete with a twinkly Merlin character played by Ralph Richardson. Also, the intermittent gore is suprisingly strong, considering that Walt Disney Productions is behind the film, along with Paramount Pictures. Otherwise, though, it's a fast-moving and uncommonly good-looking movie, with powerful settings in a brooding Welsh countryside. After several false starts, the creative team of Hal Barwood and Matthew Robbins have shown their stuff to good advantage. Now when will they set their sights beyond brainless summer fun?