The good news is that the Messiah that was prophesied about in various places by various people in the books of the Old Testament, actually came and did all the things that they said He would! Everything about the Jesus story is good news, but the fact that it is a story that starts in Genesis and goes through Revelation makes it even more impacting.
It is great news that God knew us well enough to know that we would need lots of proof, so He provided it by telling people through the ages (Adam and Eve, Abraham, Moses, David, etc.) how He was going to save His people – through a child, given birth to by a virgin, in Bethlehem, through a life spent among us, and then slaughtered like a lamb for sacrifice. When this is all supported by historical, non-biblical writers, it gives credence to Him as our Savior.
Then there’s the best part of the gospel, and that is that even death, which was viewed as the end, wasn’t able to stop Him. He overcame it just as God had planned by waking up from death and spending time with His people before going back to Heaven – more proof for those who need it. So, by beating death in His own body, He beat it for us as well, making salvation not just a great thing for this part of our life, the part on Earth, but also for the next part, the part in Heaven, where we will be able to actually see Him. That’s good news – the Gospel!