我认为他好用英文怎么说

你可以用英文表达 "I think he is useful" 来表示你认为他很有用。这个表达的来源是英文动词 "to be useful"，意思是有用，有帮助。

一些例句：

"I think he's very useful. He always knows the right thing to do." (我认为他很有用。他总是知道该做什么。)
"I find him to be quite useful when it comes to solving problems." (我发现在解决问题方面，他非常有用。)
"I think he would be a useful asset to our team." (我认为他将是我们团队的有用资产。)