THE BUYING GAME Forget Mr. Freeze. The real nemesis for new Caped Crusader George Clooney might be...Val Kilmer. Although Batman & Robin's premiere is still a month away, Clooney's six-inch Hasbro action figure, on the right, has already debuted. Its job: to outsell Kilmer's Batman Forever figurine, on the left. (The Forever line outsold Michael Keaton's Batman lines by 40 percent.) It shouldn't be too difficult. According to Hasbro's Tom McGrath, kids' appetites for the Winged One have been insatiable. The toy giant has released 118 different Batmen, pegged to the film franchise and other film and cartoon incarnations, and sales continue to soar. This time, girls may even get into the Bat act. ''My expectation is [Alicia Silverstone's] Batgirl will be the best-selling female figure we've done,'' says McGrath, who adds, ''Heroes sell better than villains,'' to explain the poor sales of Michelle Pfeiffer's Catwoman toy. But nothing sells until the actors approve their plastic likenesses something Clooney had no trouble doing: ''He liked it,'' says McGrath. ''And he loved the muscles.''