responces = resources. I made a typo. Of course oil wasn't the only reason, but it was one of the more blatant ones. Will there be an open offer to the best bidder to exploit the Iraqi oil sources? Of course not.
The rest of the reasons: to stabilize the area and influence the rest of the middle east, to crush Saddam, and others probably. In that order. Now if Saddam was more cooperative (and he would be, if there was no gulf war), like the Saudis, then he would still be happy oppresing his people. Until they grew tired of him and stormed him- it would happen eventually, without any foreign intervention.
I did not mention WMD, because there weren't any (to begin with). I did not mention (islamic) terrorists, because Saddam wouldn't let them live. He was an atheist and a dictator for crying out loud, they would only serve to undermine his rule.