SATURDAY NIGHT (SEPT. 12) BRINGS two fine original movies to pay cable. HBO presents Teamster Boss: The Jackie Presser Story (8 P.M. ET). Brian Dennehy stars in this gripping, highly unflattering portrait of the corrupt Teamsters union leader who had strong links to the mob while working as an informant for the FBI. Eli Wallach, Robert Prosky and Jeff Daniels costar in the film, which is in all ways superior to HBO's last bioflic, the muddled Citizen Cohn. Showtime counters with a flavorful suspense film, Devlin (9 P.M. ET), in which Bryan Brown plays a New York City cop and recovering alcoholic who is getting framed for the murder of a mayoral candidate. It co-stars Lloyd Bridges and—in her best performance to date—Roma Downey as Brown's Irish girlfriend. Look for a very strange cameo from Frances (The Unforgiven) Fisher.