2016 numbers should be between 2.22-2.23 million, the highest since 2013.
Peak overall year was 2008 at 3.258M
However, international passengers were 2.806M (or 2.761M if you exclude Belfast and other airports in the North).
So the international figure is gradually being clawed back.
Getting internal passengers back is probably never going to happen with direct buses to Dublin Airport and a much faster train service to Dublin City these days. Maybe an outside possibility of Belfast coming back one day, but hard to see who might operate it.