Regarding this Brecht guy: He is commonly regarded as one of the greatest German writers of the 20th century. As important to German literature as Thomas Mann or Franz Kafka. Bertolt Brecht is primarily known as a playwright, and with his ideas about an "epic theatre", he tried to disillusion the audience in order to create a reflective distance from the staged reality. With his "alienation effect", he meant to raise the audience's awareness of social grievances and of the inhumanity of capitalist society. His plays (and his couple of operas) were meant as teachings to the audience. Today, there are many people who think, that he has been most brilliant as a poet, and not as a playwright. I'd tend to agree. His poetry isn't as marred by political purpose and is supremely artistic.
I can only agree with Steril and xxhalberstramxx: Wozzeck is a great opera! The 19th century play by Georg Büchner is one of the great classics of German literature (although it's a fragment: the succession of scenes isn't completely clear), and Alban Berg is one of my all-time favourite composers.
If there is something that is clearly underrated in classical music, it is the contemporary or 20th century music. Very often, the lack of customary harmonic structure makes it austere and inaccessible, but Berg is certainly an exception. Although he belongs to the "New Vienna School" of twelve-tone composers (founded by Arnold Schönberg - Anton Webern being the third of them), who did away with traditional harmonic rules, Berg idolized late romanticist composer Gustav Mahler. Therefore Berg doesn't exactly shy away from tonality when the opportunity presents itself. There is a striking lyricism to a lot of his work (to his other opera, "Lulu", as well).
My favourite Berg composition is his last: his "Violin Concerto - To the Memory of an Angel" from 1935. If one isn't deeply moved by it, it's probably better to forget about further excursions into contemporary music.
Another absolute favourite of mine: "Fragments - Silence, To Diotima", a string quartet by Luigi Nono that he wrote for the LaSalle quartet in 1980. This is just music to die for. Okay, your mileage may vary.