wow. i've never heard rachmaninoff so badly talked about in all my life.
and im on the verge of emoti-slapping you, quite frankly, but you are new to rachmaninoff, and there's need to get angry.
first off, why i like rachmaninoff. his music is verry, extremely, expressive. fillled with passion and emotion. granted his second and third piano concerti have some of the most beautiful melodies i've ever heard, more so the second. but, i find that in his solo piano pieces is where he truly speaks to his audience. and to address the depressing comment you made. he was very much a depressed person, and unhappy (because he couldnt return to his country, he was forbidden) his etude-tableause are a generally depressive music, for me anyway, and these were not just etudes as the name suggests but pictures of himself, tableaux, within the etudes. and being the sad person he was, so was his music, but his music is also one of the most passionate i've ever heard. comparing his music to saay beethoven's sonata's, from my experience the one work of beethovens that i feel as much emotion stirr is the appassionata, but then theres also his 4th piano concerto. but with rachmaninoff, just to name a few: piano concerto 2, rhapsody on a theme of paganini, elegie, prelude op 3 no 2/ op 23 no 2/no5, moment musical no 4, etude-tableaux op 39 no 1/ op 33 no 4(or 5, whichever way u like it), the list goes on. i also love his music for its sheer complexity....yet, simplicity, i dunno if im making sense when i say that, but for those who understand me, i think u know what i mean, but i cant explain, not at 3 am anyway.
i could go on, but im pretty tired rite now, but you should really listen to those pieces i listed. the etude tableaux's and the musical moment, granted, take a second or third listening to, to really feel and understand it. but give it a shot.