According to some video retailers, "Thelma & Louise," the comedy/drama starring Susan Sarandon and Geena Davis, is the hottest rental title on the market. On the Billboard magazine rental chart, it took a mighty leap, from No. 30 to No. 5, and has a good shot at toppling "Terminator 2." Just as hot, some retailers are reporting, is the wacky spoof "The Naked Gun 2 1/2," starring Leslie Nielsen, which moved up two notches to No. 3. This one, too, has a shot at No. 1. "Bill and Ted's Bogus Journey," sure to be a male teen fave, debuted at No. 15 and may wind up in the Top Five. The small, acclaimed art film "Straight Out of Brooklyn" is doing decent rental business--up three notches to No. 21.