It isn’t one’s worship system that determines an eternal reward, but what is in that person’s heart. As to the question of the 400+ denominations that all claim Christ, most think that God will sort it all out in heaven. They think that all “Christian” churches are equally legitimate. That said, none of these churches will cross lines and fellowship with one another.
Some teach that all denominations (except their own, of course) are hell-bound. Among these are Jehovah’s Witnesses, Mormons, and Catholics, to name a few. Calvinists, who make up several denominations, think they’re chosen by God to be saved, while the rest are likewise chosen to be condemned. The Church of Christ maintains that they are the One True Church, although the criteria used is legalistic, subjective, and totally bogus. I should know, I was with the CoC for many, many years.
Some churches have the idiotic notion that if women wear pants or put on make-up, they and the church that supports them are condemned. "Look Lord, I never grew my hair long! I’m ready to enter heaven!" Bogus nonsense that reflects how fleshly they interpret the scriptures.
These people can't get it through their skulls that it isn't what one does or doesn't do—it isn't what one eats or doesn't eat—that matters with God. (Col. 2:16-19) Jesus said that many who thought they were Christians, and who were mightily engaged in what they considered "Christian service," will find themselves rejected on Judgment Day. (Matt 7:21ff) In the context, the great qualifier of who gets into heaven will be “whoever does the will of the Father.” The Father’s will has very little to do with a church’s worship model and much to do with a person’s motives and love for their fellow human beings. (Matt 25:31ff)
Thus, it isn’t what creed you hold to, what version of the bible you thump, or what name is painted on the church sign—it’s the one who does God’s will. The old verse, “not my will, but Your will be done,” is what will separate us at the Resurrection.
Jesus summed it up best: “Unless you humble yourself and become like a little child, you will not even see the kingdom of heaven.” (Matt 18:3)