Thanos probably doesn't see himself as good. His actions and goals are often seen as villainous, and he might justify them based on his own warped sense of balance and destiny rather than any sense of goodness.
I don't think Thanos thinks he's good. He believes his actions are necessary for the greater good, but that doesn't mean he sees himself as a typical 'good' character. His perspective is very unique and morally ambiguous.
I think Thanos doesn't consider himself good. He has his own complex and often destructive motives.