Jesus did not say, "Unless one is religious he cannot see the kingdom of God." He said, "Truly, truly, I say to you, unless one is born again he cannot see the kingdom of God." Nicodemus was learning that these two things were very different.
Being religious means following rules in order to gain a higher standing. Through religion there is a distinction between good men and bad men. But Being born again means there is no longer any difference between men because all have sinned and fallen short in the eyes of God. Believing this truth humbles you to submit yourself to Jesus Christ, the only one that is good and the only one that can give you right standing before God. Instead of boasting in what we do, those who are born again boast in what Jesus did.