Run-DMC did more than anyone to bring rock into hip hop in the mid-’80s. Greatest Hits shows the band at their best (the Tipper Gore-baiting “Mary Mary”) and worst (the cutesy “Christmas In Hollis”). The purists sneered at the Jason Nevins makeover of “It’s Like That”,but those warehouse visuals will have turned a new generation of suburban 13-year-olds on to hip hop.