While the fall has yet to produce a blockbuster like last year’s “Shark Tale,” this season’s crowded marketplace of mid-level successes has kept the B.O. buoyant. “Shark Tale” grossed $161 million after bowing with $47.6 million on Oct. 1. This year, it’s been titles such as “The Exorcism of Emily Rose” and “Flightplan” that have been this season’s savior … so far. No one’s expecting any giant openings from the three new wide releases this weekend, but respectable if not spectacular performances should help continue the autumn’s lead over box office in the year-earlier season. Paramount is opening Cameron Crowe’s “Elizabethtown” at 2,517 theaters over the frame, while Sony bows frightener “The Fog” at 2,927. New Line debuts Tony Scott’s model-turned-bounty hunter tale “Domino” at 2,223.