I remember when I was growing up, this was a question I would often wonder about and ask. People would say "because Jesus died on the cross!", which was of little help to me as I would then think, why was Jesus dying a good thing?
But this is a question I'm sure many people will have asked themselves when they consider the name of their Bank Holiday, and probably a question they got an unsatisfactory answer to - if they got one at all!
Really though, this holiday time should be more well-known and recognised than Christmas. While the birth of Jesus is important, it isn't actually central to the Faith, nor is it really emphasised much in the New Testament. The more complete birth narratives appears in Matthew and Luke's Gospels only; Mark skips it and John only alludes to it in John 1:14 ("And the Word became flesh and lived among us..."); and Paul too, only mentions Jesus's birth very briefly in Galatians 4:4-5 and Romans 1:3.
Basically, the early Christians didn't care about this event in the same way we do today.
And history would tell us this as well, as celebrating birthdays were a pagan/Roman tradition, the Christians had nothing to do with it. It wasn't until around the 4th Century when Pope Julius declared December 25th as the date in order to corresponded with the Roman feast of Saturnalia.
But the real celebration, and the main thrust and focus in the New Testament is the death of Jesus and his subsequent resurrection. While there does seem to be some evidence to suggest that by the 2nd Century, early Christians were celebrating Easter, it sometimes feels like the Modern Church has placed more emphasis on Jesus's birth in terms of celebrations and events, than it does for his resurrection. Though that's probably partly due to Western culture and the so-called "War on Christmas" making some churches push Christmas harder.
I digress. Paul makes his view on the resurrection, and thus the whole point of Christianity, quite clear in 1 Cor 15:12-19 (emphasis mine) —
Now if Christ is proclaimed as raised from the dead, how can some of you say there is no resurrection of the dead? If there is no resurrection of the dead, then Christ has not been raised; and if Christ has not been raised, then our proclamation has been in vain and your faith has been in vain. We are even found to be misrepresenting God, because we testified of God that he raised Christ—whom he did not raise if it is true that the dead are not raised. For if the dead are not raised, then Christ has not been raised. If Christ has not been raised, your faith is futile and you are still in your sins. Then those also who have died in Christ have perished. If for this life only we have hoped in Christ, we are of all people most to be pitied.
Verse 17 spells out quite clearly just why Good Friday is so good! If Christ was not raised, then our faith is pointless. If Christ was not raised, then there is no forgiveness for our sins.
If Christ did not die, then he could not be raised. If Christ did not die, then there was no atonement for our sins (1 Jn 2:2; 1 Jn 4:10).
And that is why Good Friday is good. Because without the death of Jesus, there is no redemptive forgiveness from God and thus no hope for ourselves.
In him we have redemption through his blood, the forgiveness of our trespasses, according to the riches of his grace that he lavished on us.
Happy Easter everyone :)