To Vietnam War-era college students, wisecracking interloper Groucho, mute sprite Harpo, and hustler Chico were poster boys for antiestablishment comedy. Today's youth seem to favor gross-outs over rebellion. The Marx Brothers Collection (Unrated, 10 hrs., 33 mins., 1935-46), while sure to bring some joy to fans, is not likely to inspire a revival. From the rapturous heights of A Night at the Opera to the desperate depths of A Night in Casablanca, this set charts the slow, sad decline of the comic anarchists. Opera and its even more popular follow-up, A Day at the Races, represent the peak of the trio's MGM period but hint at their imminent downfall. Room Service, Go West, The Big Store, At the Circus, and Casablanca all have moments that recapture the glory of the brothers' undiluted Paramount films (due later this year on DVD), but the once-wild Marxes were now decidedly tamed -- with producer Irving Thalberg insisting on comedy bits between intrusive musical numbers and icky romance. Each disc re-creates an old-fashioned night at the movies, with vintage shorts, cartoons, and trailers; commentaries by Leonard Maltin and Marx Brothers Encyclopedia author Glenn Mitchell are enthusiastic and exhaustive. Critic James Agee once said, ''The worst [the Marx brothers] might ever make would be better worth seeing than most other things I can think of.'' This collection puts that sentiment to the test.