You're right, up to a point; Jesus was innocent of any crime, and from a human standpoint He didn't deserve to die. You also are right in saying that Jesus' death was a great tragedy—for it was.
Why do Christians call the day of His death "Good Friday"? They do so because of what He accomplished for us on that day. The key is to understand who Jesus was, and why He came into the world. Jesus wasn't just another human being; He was also God in human flesh. Jesus Himself declared, "Anyone who has seen me has seen the Father" (John 14:9).
And the reason He came into the world was to deal with the greatest problem of the human race: the problem of our sins. Jesus was perfect and without sin—but on the cross all our sins were transferred to Him, and He died in our place. We deserved to die on that cross, but Jesus took the punishment we deserve—and because He did, we can be forgiven and cleansed of all our sins.
Yes, it was a tragedy Jesus had to die—and the reason He had to die was because of us. There was no other way for our sins to be forgiven, and no other way for heaven's door to be opened to us. He was willing to do this because He loves us, and He doesn't want us to spend eternity apart from Him. Open your heart to Christ today, and when you do, it truly will become your "Good Friday"!