Why is it a good theory? Because it fits closely with what we see in the universe. It's been tested and retested again and again. That's the essence of science: come up with a theory that fits what we know, then figure out ways to tear it down, prove it false. Tests are repeated again and again to either replicate the results or invalidate the experiment. The longer the theory survives, the closer to "law" it becomes.
This is why the realm of religion and belief in a creator isn't an exercise in science, but rather one of faith. There's no test to show that God doesn't exist. God isn't a theory; he's either a fact or a myth depending on which side of the question you fall.
Which brings me to my favorite secular religion: global
Read this, and try to imagine Newton saying this when contemporaries wanted to see his notes on gravity:
“We have 25 years or so invested in the work. Why should I make the data available to you, when your aim is to try and find something wrong with it?”
That's the response an Australian scientist got when he asked for the climate data gathered by Drs. Phil Jones and Tom Wigley, the authors of the first history of surface temperature, which served as the primary reference standard for the U.N. Intergovernmental Panel on Climate Change. Using this data, the IPCC declared human action had a significant impact on climate change.
Since that request, several other scientists from around the world have asked for the data and been refused. Think about that. The authors don't want anyone to try and replicate their work. That's pretty much the opposite of the scientific method.
I don't doubt that the climate is changing. I'm open to the idea that humans have a measurable effect on the climate. I remain skeptical though (ed. note: like a scientist? Yes, exactly.) For global