When asking a question about God (and especially if that question affects whether or not someone will believe in God), it is vital to take all of God's attributes into account. Take, for example, the following question: If God loves us so much, why can't He just forgive our sins? This common question emphasises God's love, but de-emphasises His justice.
It is well known that God loves us, and wants everyone to go to Heaven. But what should also be well known is that God is perfect. Every sin must be dealt with. Think of it this way: In the U.S.A., the president has the power to pardon people convicted of federal crimes, including members of his own family. But what if they actually committed the crime for which they have been convicted? In this case, love doesn't come into it. The family member is guilty, justice must be done.
God has more power than any president, but is also far more committed to setting things right. Sin must be dealt with. How can we expect God to act otherwise? But thankfully, God has more than one option. Substitution is also valid. If the innocent receives the punishment of the guilty, the guilty can receive the reward of the innocent. And so that is the option God took. Jesus was punished for our sin, and so through faith, and only through faith, we can receive eternal life.