By faith Abel offered to God a better sacrifice than Cain, through which he obtained the testimony that he was righteous, God testifying about his gifts, and through faith, though he is dead, he still speaks. (Hebrews 11:4)
Cain and, his brother Abel, both brought an offering to Lord; ... and the Lord had regard for Abel and for his Offering; but for Cain and his offering He had no regard. So Cain became very angry and his countenance fell. (Genesis 4:4-5) Cains anger because of God's rejection and his resentment of Abel finally lead to him killing his brother.
Both brothers believed in God, both came to worship Him, and both knew the sacrifice God required. But only Abel worshiped the Lord in faith and in accordance to the Lord's required sacrifice. Nothing has changed. God still requires that we come to Him and worship Him in faith and in accordance to His required sacrifice; And without faith it is impossible to please Him, for he who comes to God must believe that He is and that He is a rewarder of those who seek Him. (Hebrews 11:6)
There is only one acceptable faith and only one acceptable sacrifice; Jesus said to him,"I am the way, and the truth, and the life; no comes to the Father but through Me." (John 14:6) Are we the only Church that has the truth? No, God is the only one that has the truth and anyone who worships Him, must do so in Spirit and in truth according to His only acceptable and exclusive sacrifice-- Faith alone in the gospel of the Lord Jesus Christ. Maranatha!