Cu Chulainn said:
How do you reconcile the concept of a just god with the concept of eternal punishment?
Why does god care about our faith?
What is the most compelling reason for faith?
Why Christianity?
1) I'm not sure that you can. I'd question where we get our ideas of eternal punishment from anyway. What we call the 'Christian' view of hell is really a collection of various thoughts and sayings in the bible, and they do not all fit together... sometimes they are poetic images, used in parables, which people try and apply a literal meaning to. A few thoughts
a) The earliest Hebrew Texts don't seem to have an afterlife. On death, one literally goes to 'dust'.
b) Many of Jesus' teachings on 'hell' or punishment beyond this life were associated with justice... ie, Luke 16:19-, where the punished individual was given a tough break in the afterlife because he ignored a struggling man in this one. The point is not a literal representation of hell, but an encouragement to look out for the poor.
c) Rev 20:14 'Death and Hades were thrown into the lake of fire', seems to imply a bad end for the bad ends!!
I think the better point to begin with is God as a loving figure, in the person of Jesus... and recognise that 'punishment' is by no means a definitively clear-cut concept.
2) God cares about relationship, of which faith is a part. The Christian God, at least, is a relational being. Thus for Jesus, the two greatest commandments he could summarise from his Jewish tradition were to 'Love the Lord your God with all your heart, and with all your strength, and with all your soul, and your mind, and to love your neighbour as you love yourself'... (the exact quote varies from gospel to gospel).
3) For me, the oppurtunity to connect with the infinite... which reason and logic cannot do.
4) Why Christianity I think is the wrong question. 'Why Jesus' is a better one...
What the gospels record of Jesus is worthy picture for consideration. If there is a God worth following, the God revealed in Jesus seems to my mind to be pretty close to it... a God of hope, oppurtunity, justice, challenge and surprise. A God who gives room for dialogue, challenge, questioning, and discussion.
That message has sometimes been lost in the history of Christianity... but one can hardly go wrong in following the teachings of Jesus, rather than making Jesus follow the teaching of their tradition!