Although DVD compilations are a treat for aficionados of any beloved TV series, in the case of Stephen Cannell's ''Wiseguy'', they're practically a necessity. Its serialized structure -- in which story lines were played out in multi-episode mini-epics -- was a groundbreaking claim to fame but also a programming handicap that rendered the 1987 -- 90 CBS drama nearly invisible in syndication. In this collection, Ken Wahl stars as federal agent Vinnie Terranova, who infiltrates the Atlantic City fiefdom of Mob boss Sonny Steelgrave (Ray Sharkey, in a chilling performance) almost too successfully. As Wahl relates in a pair of audio commentaries, Vinnie discovers a sympathetic brother figure in his would-be nemesis. In Steelgrave (as well as the series' subsequent mercurial villains), ''Wiseguy'' inaugurated a new kind of filmic gangster -- brutal and sensitive, angsty and verbose -- whose lineage extends to the multidimensional sociopaths of such shows as ''The Sopranos'' and ''The Wire''.