A good reason for believing in god is a love of science, or at least a working knowledge of various scientific studies and conclusions. The best argument is the universe itself. The chance of our universe becoming as it is (ie suitable to produce and sustain us) is so small that the idea it was chance alone seems to be unreasonable. Many regardless of a faith or lack of faith say it does appear to be designed. if it looks like a duck, swims like a duck, quacks like a duck, might it not be a duck?
Another argument I would make for the reality of god is evolution (gasp, yes I went there
). Life evolving as it did, particularly human life, is an incredible thing. It's also worth noting that for reasons unexplained our brains and our intelligence went through a huge surge in a relatively small amount of time, the reason for this still unexplained. Perhaps god begat a miracle. Perhaps this was the moment we received souls, and thus distinguishing ourselves from the rest of nature. There is no explanation for the level of consciousness humans possess.
There's also the fact that life itself exists. No one can begin to explain with any solid backing how chemistry became biology. How life suddenly existed in a lifeless place.
In all the above, I submit an argument for god.