Roger Ebert was one of the first and loudest cheerleaders for Steve James’ epic doc “Hoop Dreams.” Nearly two decades later James returned the favor, gifting Ebert his own doc — a loving but honest valentine to one of cinephilia’s greatest champions. James doesn’t hide from Ebert’s demons, notably his youthful functioning alcoholism. Even his storied wit could be venomous, unleashed upon not only films but his longtime frenemy, Gene Siskel. Speaking of which, “Life Itself” is at least as revealing about Siskel, whose insight and warmth has often been overshadowed by his more prominent and cinephilic TV co-star. Along with the YouTube-enshrined bouts between the two between takes of their show, “Life Itself” also includes one of last year’s most delightful images: a picture of Siskel rocking a ’70s ’stache while standing shirtless with a similarly clothed Bunny at the Playboy mansion. You’ll never see his beloved “Babe: Pig in the City” the same way.