"I am good" in Chinese
We never answer “我好” when asked “你好吗?”. Indeed, these days it's not very common for people to greet others with “你好吗？” face to face, but simply “你好” will do just fine. When greeted with “你好”, we can acknowledge it with the same “你好”. 我很好 sometimes means I am ok (so don't worry about me). Imagine two lovers just broke up but still treat each other as friends. In their letters later on, one may write 我很好，不用担心我. This is the scenario that popped into my head when I first saw this quesiton.