Safety is just like a financial investment, past performance is no guarantee of future performance. And cutting to the chase, what passengers really want to know is are they going to end up in a smoking hole on their next flight. The more cynical of us might believe all airlines want to know how little can they spend on training and safety related activities to avoid the smoking hole. Governments want to know how just little they can do avoid any responsibility for any smoking hole on their patch. Journalists love smoking holes because they give them something to write about.
So what makes a safe airline? Firstly one that is prepared to invest in selection and regular training. Next, one that is prepared to support its staff in their day to day operations and never punish genuine mistakes. A safe airline will also have a strong trade unions that are prepared to identify risky and unsafe practices. Then that airline must be properly monitored by a genuinely independent oversight authority, one that is not dependent on the airline and is free from political interference. Finally, when things go wrong, which they will, a proper reporting and investigative process so we can learn from our past and try and avoid the smoking holes of the future.
With a few exceptions, the safest will be first world airlines. However, reality means no airline will ever be 100% safe.