A Christian atheist?

This might not be the kind of words you would expect to read on the blog of an atheist, so brace yourself:

I like Christianity. I like it very much. In a sense, I feel I am mildly Christian.

Don't get me wrong, I also hate Christianity, and in many ways, I cannot stand religion. So let's clear a few things up.
I certainly do not believe in God, but contrary to what an irrelevant, ancient book suggests, I doubt that really matters.  

See, at the heart of Christianity, and indeed most of the mainstream religions, there is a message that I could not agree with more strongly.
It is a message that preaches kindness, generosity, loyalty and compassion.

I think that's excellent. I hate the way the world has become a selfish, money obsessed cesspit with a disgusting mainstream culture of greed and narcissism.
I think we should all make an effort to be kind, and selfless and generous.
At the moment, if you try to be always kind and selfless and generous, it will get you nowhere, because people find it far too easy to take advantage of you. So instead we all have to descend into the same level of cynicism, and we all have to look out for ourselves, and ourselves only.

So, morally and ethically, I fundamentally agree with the message of Christianity. Help people. Be kind. Be generous.

But what I don't understand, is why these concepts have to be tied into the idea of a God.
The Bible and the teachings of Christianity often offer wise advice, strong moral stories and the uplifting idea that humans doing good to each other can only be a good thing.

Why does there need to be a power-hungry Santa Claus figure at the top of the pyramid who demands that the most important thing that you do in your life is believe in him?

Why would it matter if you believe in him or not?
Say you live a kind, selfless life but you don't ever believe in God, you don't go to church and you don't pray. You don't do those kind selfless things because you want to improve your chances of getting into Heaven for eternal bliss. You just do them because it's the right thing to do, and you feel good when you do good.

Why would it matter if you're wrong at the end. You die, and God pops up and says "yeah, I do exist, you were wrong not to believe in me".
It wouldn't change the fact that you lived a good, kind, selfless life.
If anything it makes it more noble.

Christians who believe in God (and it works for most religions) can justify their good deeds because they are getting something out of it.
I'm not expecting to get anything out of being nice to people.

I don't believe in God. But I think that if he does exist he would rather I do good things and not believe in him, than do bad things and completely believe in him.