Airbus and Boeing have been waging a competition for the single aisle market since 2013 with its respective NEO vs Max Version. Overall, including the CEO and NG backlog for market share relationships Boeing edges Airbus in the NG category. Airbus hold an undeniable lead for the single aisle class with orders. Mainly having a huge lead with its A321NEO model. This chart is not complete as the order intake is very fluid and data for the Single aisle represents the last known update.
However, it does show a relative 60-40 market split for which Boeing hopes to narrow during 2016, bringing the market difference to a 50-50 competition. Boeing would need to gain about thousand more than Airbus for the program history. I am going to assume that Boeing will chip away at the Airbus single aisle lead and will catch them in sales by 2020.