“Gladiator II” asks the question: Are you not moderately entertained for roughly 60% of this sequel? Truly, this is a movie dependent on managed expectations and a forgiving attitude toward its tendency to overserve. More of a thrash-and-burn schlock epic than the comparatively restrained 2000 “Gladiator,” also directed by Ridley Scott, the new one recycles a fair bit of the old one’s narrative cries for freedom while tossing in some digital sharks for the flooded Colosseum and a bout of deadly sea-battle theatrics.