Suppose that Jesus, having died on the cross, had stayed dead. Suppose that, like Socrates or Confucius, he was now no more than a beautiful memory. Would it matter? We should still have his example and teaching; wouldn’t that be enough?
Enough for what?
Not for Christianity.
Had Jesus not risen, but stayed dead, the bottom would drop out of Christianity, for four things would then be true.
First, to quote Paul, 1 Corinthians 15:17: “if Christ has not been raised, your faith is futile and you are still in your sins.”
Second, there is then no hope for our rising either; we must expect to stay dead too.
Third, if Jesus Christ is not risen, then he is not reigning and will not return and every single item in the [Apostles'] Creed after “suffered and was buried” will have to be struck out.
Fourth, Christianity cannot be what the first Christians thought it was—fellowship with a living Lord who is identical with the Jesus of the Gospels. The Jesus of the Gospels can still be your hero, but he cannot be your Savior. . . .
[Jesus' resurrection] marked Jesus out as Son of God (Romans 1:4); it vindicated his righteousness (John 16:10); it demonstrated victory over death (Acts 2:24); it guaranteed the believer’s forgiveness and justification (1 Corinthians 15:17; Romans 4:25), and it brings him into the reality of resurrection life now (Romans 6:4).
You could speak of Jesus’ rising as the most hopeful—hope-full—thing that has ever happened—and you would be right!
J.I. Packer, Growing in Christ, pp 59, 61 (paragraph breaks and emphasis mine)