Despite the success of “The Avengers,” summer domestic box office has been rocky this year and is trailing 2011 by approximately 2%. But a pair of major players entering the fray — “Madagascar 3: Europe’s Most Wanted” and “Prometheus” — should help close that gap.Paramount-DreamWorks Animation’s “Madagascar 3,” bowing today at 4,258 locations, is expected to land at most $65 million through Sunday. That would be enough to trounce Fox’s Ridley Scott sci-fier “Prometheus,” which some tracking services have pegged for an opening of $40 million-$45 million. Even one of those perfs would far exceed last year’s top player, “Super 8,” which opened this same weekend at $35.5 million. That said, the perfs of “Madagascar 3″ and “Prometheus” are especially hard to predict. For starters, the openings of family films are notoriously difficult to forecast since young kids don’t figure into tracking, while “Prometheus,” which spiked with males on Thursday afternoon, could split other demos, depending on existing enthusiasm for the “Alien” franchise. “Madagascar 3″ kick-started what will likely be a strong weekend overall internationally, bowing Thursday in Russia with $3.7 million — the biggest opening day ever for an animated pic in that country. The toon bows day-and-date this weekend in 29 overseas markets, including China. “Prometheus,” meanwhile, cumed north of $54 million through Wednesday, with an additional 35 markets set for openings this weekend including Australia, India and South Korea. Domestic holdovers will further boost weekend totals, led by Universal’s soph-sesh player “Snow White and the Huntsman,” which looks likely to drop 55%, an OK hold for summer play time, for a weekend take of $25 million. “X-Men: First Class,” for instance, fell 56% in its second outing. Most of the summer holdovers haven’t performed compared to last year, when five films had earned north of $100 million by this time. So far, only two pics — “The Avengers” ($559 million) and “Men in Black 3″ ($119 million) — have reached that domestic marker this year. If “Madagascar 3″ bows at the high end of expectations, the toon would see the franchise’s best debut, besting 2008′s “Madagascar: Escape 2 Africa,” at $63.1 million. But Par has lower expectations comparable to the first film, which opened to $47.2 million in 2005. The sequel, at $180 million domestically, wound up cuming $10 million less than the first, which doesn’t necessarily bode well for the $145 million-budgeted three-quel Stateside. The toon’s 3D format will increase grosses globally, however. “Madagascar 3″ is the series’ first stereo installment. The same goes for the 3D “Prometheus,” which according to Fox cost $130 million, though other sources say it’s higher. The film launches at 421 worldwide Imax locations, of which 298 are in the U.S. and Canada. Fox spent considerable effort early on distancing R-rated “Prometheus” from Scott’s 1979 “Alien” pic, but the studio has since relented by relating the two films in marketing materials. That should draw die-hard supporters of the franchise; word of mouth and reviews will be essential for attracting non-”Alien” fans. At the specialty B.O., meanwhile, IFC launches Jane Fonda family dramedy “Peace, Love and Misunderstanding” at 28 locations, while Magnolia’s Robert Pattinson period drama “Bel Ami” bows at 16. A pair of other comedies bow in limited release: FilmDistrict’s “Safety Not Guaranteed” at nine Stateside locations, Fox Searchlight’s “Lola Versus” at four.