Content marketing is all about helping your customers and avoiding sales-like language.
In order to attain marketing success, you must create content that is helpful and relevant to your customers and authentic and pertinent to your brand. Your goal is to establish a trusting relationship with customers and prospects. There are also the obvious points of making sure that the content is written well and free of grammatical errors and typos, etc.
Then, there's "bad" content, which can be identified by sales-type messaging. In other words, if you want to create good content, don't tout your products or services, because your prospects and customers are more interested in what you can help them with. They don't want to read copy about how awesome your products/services are or why they should choose your company. They're looking for information that can help them to make their own decision(s).
So focus on educating, not selling. I can't emphasize that enough. Try to think about your marketing efforts from your target audience's point of view, and go from there.