Winning anything? Is that always at someone elses detriment? Are you saying that because there are winners, there must always be losers? Because i would argue that winning something doesn't cost the ones that didn't win anything. We all started at the same point. As losers (or not winners), they have the same that they did before. Only the winner sits at a different state.

If my gain causes suffering of others, then even though i would be happy about my gain, it would still be wrong to cause that suffering to others.

Even animals have an understanding of morality. It is not limited to humans. Its just more pronounced and debated.