S.T.A.L.K.E.R. Shadow of Chernobyl

What other endings are there, how can I view them, and what are the requirements for unlocking them? Regarding the game being short, that was a bit disappointing. I wasn't really looking forward to it, I just saw a preview on Igromania (a long time ago, maybe 2 years ago or more). They presented the game as a huge open world, showed a quest for an artifact, and said it would take a long time. What the developers did particularly well was the sky. It's not exactly beautiful (gray clouds like before rain), but it's made so realistically that it's almost unsettling. Now I'm waiting for the expansion, hopefully not for another 8 years....