My favorite arguments for the existence of God:

The teleological argument. We can see the difference between a lifeless object and a living one and since we've discovered our own ability to create, theres a remarkable complexity to living organisms that we assume that it must have been created. A bunch of sand on a beach isn't just going to turn in to a working clock.

(I don't know the fancy names of these next 2)

The concept that many different civilizations before us, completely independent of one another all had a concept of Gods in some form or another. Like we were pre-programmed to believe in religion. Even now, despite all logic and reasoning brought in to the world, people naturally trust religion.

The concept that there are many levels of intelligence before us, and who's to say there are not higher ones then us that we just can't understand like an ant trying to understand humans.

Now that I've covered that, let me tell you my problems with Christianity. (Why do I pick out Christians? It's because it's the religion I know)

Now, assuming that since the modern western world was founded on Christian values, then there are a few fundamental problems I have with Christian beliefs.

The idea that people get their just rewards in hell. Far too many times I read in the paper about how killers and child molesters are released and recommit these crimes. The idea of forgiveness is a very good one, but there needs to be some punishment in this world because we really don't know what lies in the next one.

The idea that life is just a small stage until one gets an eternity in heaven. It bothers me that western values have been established in the way that we trudge through life just making our way to the end where the real fun begins. We should be enjoying life as much as we can.

The concept that the world will be destroyed. It bothers me when people talk about our inevitable end. If a meteor is detected to hit the earth, what would happen if everyone believed that it was God's way and we didn't do anything to stop it? Many generations have believed that the rapture is coming in their life time, and this led to many mistakes, like the Crusades. Many people in powerful places have probably made bad decisions in the belief that they can't possibly destroy the world, that only God has that power. There are many global warming deniers that remain firm in the belief that humans do not have the ability to destroy our own world.

Christianity doesn't deliver any purpose. The only ones that I heard of were to be a good person and spread the gospel. If there is a creator then what is our true purpose? If something is infinite in power, then why does it need us? Are we it's pets? Is our purpose simply to lead an entertaining life for our designer? Are we just a harvest, yet to be harvested? Are we in some kind of race? Are we supposed to technologically advance?

I would think that we are. I would imagine that if I made something, I would be more proud of it's achievements in the universe then it worshiping me.