The most common success patterns are surprisingly simple in theory yet hard to balance for some brilliant people. The following is my top 5 but certainly not conclusive list.
1. Entrepreneur Spirit. The APM/PO is the team(s) leader. She is acting CEO, protecting the company's product or services as if it were her own money being investing.
2. Leadership. Takes responsibility and leads by example. Facilitates the best possible course of action and garners buy-in from the right people. Self-aware and able to make decisions.
3. Inspirational. She is the most excited person in the room and glimmers with passion for the product vision. Always ready to back up decisions with convincing evidence and respecting opinions when provided.
4. Customer centric. The APM/PO doesn't neccessarily need to be the expert in all things, but understands the need for experts in customer journey mapping, user experience design, market research, customer trials and feedback groups.
5. Organized. Understands the process and aligns herself to the best possible business outcome. Coordination between large groups and getting results out of a large system requires skills and knowledge of the process.
Some folks might be thinking I forgot to include knowledge about the product. I think this is important but I think a great APM/PO leverages the expertise of those that are closest to the subject. One cannot be an expert at all things but one should have the wherewithal to make smart decisions immediately and when to facilitate feedback for riskier decisions. After all, shouldn't we all be listening to the market and other reliable sources of intelligence? Shouldn't we never stop learning?
So what makes a good agile product manager/product owner? Someone who can balance their act between the 5 patterns listed above. Some organizations are not mature enough for the highly evolved APM/PO, so organizational skills are valued more than inspirational. Some organizations are trying to disrupt the market so the entrepreneur mindset is more attractive than someone who follows process.