To throw egg on the Elvis argument, you can disprove Elvis is still alive by digging up his grave unless they cremated his body.
Since you can't disprove God's existence and assuming he is the one to cause the big bang, for all we know he essentially wrote the laws of physics, it is believed that people have the power to make their own choices.
As you say if God exists why does evil exist, well if no evil existed would people know what good is?
Human lives last less than a second as far as time in the Universe goes, for all we know that evil will end up triggering an event later that will put a stop to that evil and accomplish a great good that wouldn't have happened if that evil event hadn't happened. Point is just because things seem to have no point, doesn't mean there isn't a larger force at work.