This is a very large question requiring a very large answer. You must consider all the major religions and what is behind them because worship comes in many forms for many different reasons. I can only give you one idea of what worship is.
To me, in Christianity, it’s not about the music or the waving of hands or the tripping and falling all over the place to please God. I don’t worship like that. When Jesus prayed, he did not do those things anyway.
Getting on with the topic, Jesus died for the sinners of the world, past, present, and future. Otherwise we would all be in Hell or going there – there would be no hope. No other major religion offers that kind of pardon on humanity. This is why we worship. Not because we are literally afraid, but because we are thankful.
Also, for me, God is at the center of life, so I try not to make anything else the center. What I chose to do in life, it had better be with Him in mind. So, worship is a way of life. It is adhering on a daily basis to a set of values (and morals) from people who have already experienced it. Though no one is perfect in this, we do our best to live by this model.
It is not about doing all the good work we can in the world, either. We are not perfect. That’s not worship. It is about how strong our faith is. I think for any Christian living a life in worship – that is the most fulfilling way to live. (I think I described it as best as I could).