Well, the question is: Once you have accepted that a god exists, what attributes must He/She possess?
My own reasoning has lead me to believe that God must have certain attributes or else be wholly unworthy of love, respect, and worship. I rejected the non-monotheistic religions as being far too fuzzy to me. It made no sense that there would be multiple supreme beings or that a single supreme being would tolerate other uber-powerful beings to bicker with each other, etc... From a philosophical standpoint, it all seems too silly. So, if I were to accept the existence of a god, it had to be one god.
So, what attributes does he/she have? Take, for instance, the old philosophical dilemma "The Problem of Evil"... how can God be all powerful, all good, and still have evil exist? My answer is that God is not all powerful... since I know that Evil exists (being a student of history and having seen it myself in my own life) and because a god that is not all good is not worthy of worship, so I reject that notion. An all-powerful God that allows evil to exist is just sadistic.
Of course, popular Christianity tries to maintain contradictory notions of God and explain these contradictions away by saying the "God is mysterious". So, I reject popular Christianity. But popular Christianity is based on the Nicene Creed, the absolute worst collection of self-contradiction and meaningless confusion ever devised by man. So I reject the Nicene Creed.
But if God is not all-powerful, then why worship him? Well... I'll get to that...
In rejecting the Nicene Creed, I also reject the notion that God created us... I mean I accept that he created certain aspects of us (spirits, bodies, etc...), but the part of me that I consider most inherently "me" God did not create. If he did, then he would be responsible for everything I did, not me. If I choose to follow him, he designed me to do so. If I don't, likewise... so if that were true, why would one person be punished and another rewarded, each for doing nothing more than what they were designed to do?
After looking at these attributes of God, I consider what is God's purpose then? Again, I reject the Nicene notions that He created us "for his own good will and pleasure" (that seems highly ego-centric to me).
So, I am left with only one set of answers:
1. The universe self-exists (i.e. God did not create the universe) and there are rules that govern the universe to which even God is subject. This clears up a lot of confusion and problems with the classical views of God. Yes, there was a big bang, yes the laws of physics rule, etc...
2. We self exist. Otherwise God is cruel, capricious, and sadistic.
3. God's purpose must be to assist mankind to attain our highest potential through self-awareness and personal growth. Indeed, I think God is trying to make us like him.
It is that third point that I think makes God worthy of worship. His intentions are not to mete out rewards and punishments, but to lay out a road map that if we follow will help us to become gods ourselves.
The reason I accept Christ as the means by which this is accomplished is because it is in his doctrine that you find each of these ideas espoused (if not overtly, by implication). My religious view centers on Christ because I believe that more than any other religious figure, he espoused the personal growth that I'm talking about and never tried to subjugate his followers underneath him. Indeed, he encouraged his followers to "be perfect, even as your father in heaven is perfect." That is pretty lofty stuff.
Most religions do not make such a philosophically pleasing assertion. Except the one to which I belong.