Most said stuff like altruistic… but greed doesnt necessarily mean to want something off others. You can be greedy for money… for performance, pleasure, or anything…
Altruistic and selfless are actually the opposites of selfish and self centered. Also generosity is the opposite of thrift.
I believe the opposite of greed (and what you should be… because greed is dangerous) is Contempt. That is contempt with what you got, happy with what you have. Its called contempt. Greed is risking what you already have to get more of it… and it can hurt.