Oh, what a famous phrase from Matthew 22:14! It is commonly used to tell people in general that salvation is very difficult and only for the few.
I favor a closer reading. When we look at all of chapter 22, plus chapter 21 coming before and chapter 22 coming after, we find Jesus vehemently and fiercely condemning the outwardly called: the chief priests, elders, and Pharisees. I propose that in the phrase "many are called, few are chosen," the many are the religious insiders.
Thus, the warning here is very precise: you who are the called, the religious elite, very few of you will be chosen for the wedding feast. How then should we apply the passage today? As Christians, we are now the religious insiders. The passage is a warning to us, especially to the Christian leaders among us, our versions of the chief priests, elders, and Pharisees. Many of us religious insiders are called, few are chosen. Moreover, the shorter version of this parable in Luke 14 is very explicit in targeting the rich and exalting the poor and marginalized. Again, insiders are targeted; and outsiders are preferred. A very "Pope Francis" approach. A natural observation is that, in the time of Jesus, the religious elite was in fact also wealthy, compared to the crowds that followed Jesus.
In my view, this interpretation best takes into account the original audience vehemently targeted by Jesus' saying and is most consistent with the surrounding chapters. It is a different focus from what many think--it is not aimed at the Gentiles or non-believers of that time, but at the ones who thought of themselves as the most chosen of all. As you can see, the depth and richness of the Bible is inexhaustible. We have to be very careful not to make it too simplistic or too abstract and ahistorical.
(Public domain image)