Things can be fun, but still be bad for us. It would be fun to eat nothing but steak and cheeseburgers, three meals a day, every day. Wouldn't it? I think it would - right up until I died of a heart attack by my 25th birthday. God cares about you, and because He does, He tells you not to do things that aren't good for you to do.
Do you really think doing drugs is a smart decision? It hurts your body, and that's not opinion, that's a medical fact.
And "the universe just was" is a better argument? I don't think so. I can't see how something as vast as the universe is just came into being by itself.
As for your question about who created God, it's like this: You say God must have been created by someone - but that assumes causation, that there was one thing, then there was something different. That implies the passage of time. But before God created the universe, there was no time - and thus no causation, or creation. Before the universe was created, it was only God, for the simple reason that without time, you can't have a series of events, like the creation of something.
If God exists, (As CivGeneral and I believe) why would it be wrong to fill our lives with His love and His work? You start from the assumption that he doesn't exist, and then question why we act the way we do. I suggest you try looking at it from the opposite view, that God does exist, then maybe our actions will make a lot more sense.