Jesus taught us to love one another, to love God above all else, and to love ourselves. That message is the same across all Gospels.
Mark was the first Gospel written around 60 CE. The format of Mark is like a Greek play where we are both spectator and participant, and in the end we are supposed to finish the story. Even though we know from the beginning about Jesus, the characters in the Gospel don’t and they try to stop him before something bad happens.
Matthew was written around 80 CE. It is the first Gospel in the Bible because it is the longest and considered the most beautiful. Matthew was writing for people with a strong Hebrew tradition so they could see Jesus fulfilling the promises of Moses and the prophets. Matthew was concerned with people making sure their own behaviour was what Jesus would want before they started sharing their faith with others.
Luke is the ‘social justice’ gospel, and written around 90 CE. People used to assume Luke was a doctor because there were so many healing stories in that Gospel, but now the writer of Luke is seen as an historian. Luke is more interested in the actions of faith, and there is almost always a man’s story and woman’s story together, showing that Jesus came for everyone.
John was written around 100 CE, and is different from the other Gospels in that the stories are episodes of Jesus ministry, not a continuum from the beginning to the end of Jesus’ ministry. It is considered the most theological Gospel. Unlike Matthew, Mark and Luke, the Jesus we meet in John knows exactly who he is and what he has to do.