“The Amazing Spider-Man 2” (PG-13, 142 minutes, Sony): This sequel is a strenuously chipper but nonetheless saggy, baggy and mostly ho-hum addition to the Spider-Man canon. What was once its greatest strength – its casting – is on the verge of becoming its biggest liability. Whereas the chief pleasure of the first “Amazing Spider-Man” was the cuddly chemistry between Peter Parker (played by Andrew Garfield) and his girlfriend Gwen (Emma Stone), here they generate fewer sparks than questions. Namely: how a 30-year-old and 25-year-old (respectively), despite their proven and prodigious talents, can be expected to play recent high school graduates with any degree of credibility? Contains sequences of sci-fi action and violence. Extras include commentary from director Marc Webb, deleted scenes and Alicia Keys’ “It’s On Again” music video. Also, on Blu-ray: a six-part, behind-the-scenes making-of documentary and nine additional deleted scenes (including “Peter Meets His Father”). 3-D version also available.