商业is more like the word "commercial". You can use this word when you are talking about the "commercial activities"(商业活动). This word is morw used in business reports or official reports.

生意 I think is "business". Like 今天生意好吗？(Was the business going well today?)--when you are a shop owner or something.

业务 is used in office more. It's about office desk jobs or sales. 今天业务量很大，大家都很累了。(Everyone is tired cause today got a lot of work.)  Or a vocabulary 业务员(salesmen)--they go out, find customers and sell things.

Hope my explanation helps!

Ruby Lu

商业〉生意〉业务