Is there any chance that Gentiles were saved before Christ? Based upon what? Judgment of God? On works? Abraham's Bosom until the Great Judgment?
The book of Jonah has the answer to your question. Jonah was a prophet of God (Jonah 1:1; Matthew 12:39). God had asked Jonah to go to the city of Nineveh and preach to them (Jonah 1:2; 3:2). Jonah 3 very briefly describes Jonah’s message and then tells us that the people responded by repenting and believing in God (Luke 11:32). They believed and were saved.
Salvation has never exclusively belonged to the Jews. The great chapter of faith is found in Hebrews 11. This chapter names many men and women who are examples to us of men and women who believed in God, were saved, and went to heaven. Heb. 11:23-26 reveals that Moses knew about Jesus Christ,
By faith Moses, when he was born, was hidden for three months by his parents, because they saw he was a beautiful child; and they were not afraid of the king’s edict. By faith Moses, when he had grown up, refused to be called the son of Pharaoh’s daughter, choosing rather to endure ill-treatment with the people of God than to enjoy the passing pleasures of sin, considering the reproach of Christ greater riches than the treasures of Egypt; for he was looking to the reward. (NASB) Heb. 11:23-26
This reveals that the Old Testament prophets knew about Jesus even though He was not specifically named in the Old Testament records.
Among the list of the great Old Testament saints who are examples of faith, we find a Gentile. The Gentile is a woman named Rahab.
By faith Rahab the harlot did not perish along with those who were disobedient, after she had welcomed the spies in peace. (NASB) Heb. 11:31
James 2:20-26 tells us that she was saved. She was saved before the time of Christ, when the Israelites entered the promised land. In James 2, God explains that true faith results in good works. He says that good works are the proof that we belong to Him. Then He adds this,
In the same way, was not Rahab the harlot also justified by works when she received the messengers and sent them out by another way? (NASB) James 2:25
The people of Nineveh and Rahab were all Gentiles. They were saved before Jesus Christ was born into this world. So the answer to your question is, “Yes, Gentiles were saved before Jesus Christ.”