Yes we do. Evolution selected for the greedy. An exception might be organisms who're newly introduced into an environment and there are still too many resources for their needs so they can sit around not trying hard to get whatever they can. Once populations stabilize though, they have to fight to survive.
While that is true, different species could have different thinking patterns, and therefore different propensity to prioritize their own greed before other interests and motivations when making choices.
I'm just spitballing here, but the fact is that until we meet some other similarly advanced species and get to know their psychology, we can but theorize.
