Rousseau believed humans are, fundamentally, good and noble beings; we do what we believe is right because it promotes happiness, not because we are told to. We make mistakes, but that is natural, and it helps us learn. He believed we are inherently good people, but some of us lose it along the way. No-one believes they are truly evil or do evil for the sake of it, unless they are mentally insane, in which case they are not in full control of themselves. According to him, a utopia can be achieved if everyone acknowledges their inherent love and generosity.
Hobbes believed humans are, by definition, cruel, greedy and evil beings; we do things that will be of benefit to ourselves, and only do good if we can achieve something from it. We make mistakes because we do not care for others. He believed we are inherently selfish people, and that there is no such thing as true goodness, just a label to boost one's ego. According to him, a utopia cannot be achieved, because people are untrustworthy and incapable of compassion and friendship.
I believe in the fomer.
I am an idealist.