The gods can either take away evil from the world and will not, or, being willing to do so cannot; or they neither can nor will, or lastly, they are able and willing.
If they have the will to remove evil and cannot, then they are not omnipotent. If they can but will not, then they are not benevolent. If they are neither able nor willing, they are neither omnipotent nor benevolent.
Lastly, if they are both able and willing to annihilate evil, why does it exist?
The Greek philosopher, Epicurus, expressed those thoughts in his collection, Aphorisms. What he was addressing has since been succinctly become known as the problem of evil. Epicurus lived from about 341 BCE to 279 BCE, and in the 2.3 millennia since, no philosopher, theologian, thinker, priest, preacher, or shaman has been able to resolve the issue. Attempts to do just that are known as theodicy.
Given the existence of what we call evil in the world, it makes an omnibenevolent and simultaneously omnipotent god an impossibility. Any human being who knows in advance of a crime that is about to be committed and has the power to stop it, yet stands idly by is an accessory to the deed. With that standard, God as described by most religions is the greatest criminal accomplice of all time.
Let's look at one fairly recent example. Let's suppose that you knew that Timothy McVeigh was headed toward Oklahoma City in a truck full of explosives to park it under the day care center at the Murrah Federal Building. Let's also imagine that not only do you have preknowledge of the plan, but that you had the power to stop it. Not only that, but at absolutely no risk to yourself. Given that set of facts, if you sat idly by, didn't get people out of the building, didn't stop McVeigh, would you not have the blood of 168 victims on your own hands?
That is a high toll, yet it is a mere drop in the ocean of death and destruction needlessly caused by acts of man or acts of nature. Not only have human beings killed millions upon millions of their own, nature does an outstanding job of dealing death as well. From earthquakes in Iran, to Hurricane Katrina, to the deaths of over 200,000 in the tsunami of December 2004; natural calamities have no feeling or intent; no malice or altruism. They just happen.
Isn't this just what one would expect in a universe without a god? The universe doesn't care what happens to us, we just get in the way sometimes. The only ones who care about humanity are people themselves, and all too often, they don't care either.
So, I have to ask my religious friends, what would be different from the world we have if there were no god? I submit there would be no difference, as it is readily apparent that gods, devils, angels, demons, and the like are mere constructs of the human mind. Salvation is not coming from above, but from the efforts we ourselves put into making this little spot in the universe a better place. The best way to start is to abandon the provincial concepts of "my god is better than your god, mine is the TRUE one, yours is false", and instead work toward a world where we take care of each other. No one else is going to do so.