A collaboration between Aardman Animations and Sony Pictures Animation, “Arthur Christmas” promised to be a family picture of a different sort: a combination of quirky British humor (Aardman created “Wallace & Gromit”) and slick American production (Sony produced the recent film “The Smurfs”). It doesn’t quite deliver on that promise — but it’s an above-average, fun family feature nonetheless. With the voice talents of some of the best of Britain, though, “Arthur Christmas” could have been really special. James McAvoy is the title character, the younger son of Santa (Jim Broadbent) — and so destined never to become Santa himself. His older brother, Steve (Hugh Laurie), is heir. While waiting for the old man to retire, Steve’s streamlined the operation, retiring the old-fashioned sleigh of his Grandsanta (Bill Nighy) in favor of a technologically advanced spaceship controlled by an army of elves.