But the fact that there are so many versions and interpretations of the Christian gospel doesn't mean that the real thing doesn't exist. It exists, and although it would take (and has taken) thousands of volumes to even approach a full understanding of it, the gospel is still so basically simple that it can be explained in a single verse of scripture.
Of course, different people calling themselves Christians might choose different verses! One group says that "the gospel" is Acts 2:38: Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost. That's a great verse, but it's no more "the gospel" than today's baseball standings. Most Christians would automatically (and somewhat thoughtlessly) say that the gospel is contained in John 3:16: For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life. Well, that's a lot closer, but it's still not the complete gospel.
There have been all sorts of attempts to reduce the gospel to a simple presentation: brief sermons, booklets, and tracts. Some of these are very good; some of them are unimaginably bad. But really, the gospel isn't terribly complicated. Like any part of the Bible, it might be hard for some people to believe; but it's not hard to understand.
Here's how the Apostle Paul described it: Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand; By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain. For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures; And that he was buried, and that he rose again the third day according to the scriptures (1 Corinthians 15:1-4). There's more historical information in the following verses, referring to the people who saw Jesus after the Resurrection; but that's the guts of the gospel: Jesus died, He died for our sins, and he arose from the grave, physically, with the scars showing, according to the scriptures. None of this "spiritual resurrection" nonsense: that's just religious doubletalk.
But that's not all of it: that's just the guts. Because that passage doesn't explain how we can avail ourselves of His great work. He said, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God (John 3:3). And John said, in the first chapter of His Gospel, But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name: Which were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God (John 1:12, 13).
John 3:16 is a great verse. But it doesn't say anything about how Christ's death helps us. It doesn't even mention the Resurrection. We need a verse that gives us the whole story: and, by the grace of God, we have one.
How do we receive Christ? How are we born again? Simply by acknowledging our helplessness and our need, asking Him to forgive us, and save us. If we take one baby step toward Him, He'll come running down to meet us. But first, behind the scenes, throughout our lives, His Holy Spirit has been drawing us, preparing us for that moment. (This can get very theological, but we're not going in that direction. This is real life, not theory.)
If you want to see the gospel in one verse, here it is: For Christ also hath once suffered for sins, the just for the unjust, that he might bring us to God, being put to death in the flesh, but quickened by the Spirit (1 Peter 3:18).
Is that clear? (To some folks, it might be more clear than they'd like!) All the elements of Paul's gospel, in 1 Cor. 15, and Jesus' command to be born again, are present in that one verse. Ask yourself some questions.
Who has suffered for sins? Obviously, Jesus Christ. Not Buddha, not Muhammad, not Mary, not Joseph Smith: Jesus Christ, and Him alone.
How often did He do it? He only had to do it once, at Calvary: as He died, He said, It is finished (John 19:30). He doesn't need to be re-crucified by a Catholic priest every week in a "sacrifice of the Mass." It's done.
Who's "the just?" Why, it's Jesus, obviously: the only good and just man Who ever lived. (Mark 10:18)
Who's the unjust? Come on now! That's the easy part. Go look in the mirror! (Romans 3:10, 23)
Why did He do it? To bring us to God. No other reason.
How did He accomplish it? Just like Paul said, back in 1 Cor. 15: by dying, and rising from the dead.
That's the gospel, and it's encapsulated in that single verse.
Thank God for what He did for us, and praise Him for making it so clear to us! What a Saviour!