Jesus died on the cross and he was buried. Just the fact that he was buried is somewhat miraculous—normally criminals were just tossed in the trash heaps and were eaten by the dogs (I know, it doesn’t fit our sense of dignity but it was a 1stcentury reality). That Joseph of Arimathea went to Pilate to ask for the body is also somewhat miraculous—normally you didn’t identify too closely with a person who was just crucified.
Of course, the true miracle is that he rose from the grave. Jesus demonstrated the veracity of who he is by his resurrection, which he had previously predicted. The resurrection assures us we can have a forgiveness of our sins, and it assures us that we too will one day be transformed to have glorious bodies (1 Cor. 15).
In celebrating the resurrection we are celebrating true life which will last for all of eternity.