Seven months ago, industry observers thought Gladiator II would be the big winner. Here’s how the Roman combat epic lost its early advantage. Photo-Illustration: Vulture; Photos: Paramount, Giles Keyte/Universal Pictures To use the topically appropriate set of metaphors: Wicked cast a spell on North American audiences over its opening weekend in theaters, pulling in $114 million to wipe the Colosseum floor with Gladiator II . The swords-and-sandals sequel to R idley Scott ’s Best Picture–