Some might say that we have a greater purpose in life, or something else wishy-washy like that; but honestly, I believe we're here just cause of chance. The meaning of being alive is to find your own meaning in it, to do what you want and try to enjoy your life.
If you haven't found something you can be good at, then you haven't tried enough things, or you haven't put in enough time. If you keep working at something, chances are you'll get pretty good at it; I know how easy it can be to look at the "talented" or skilled individuals and say "I'll never reach that level", but most of the time, those people have put in tremendous amounts of effort and time into what they do, so you shouldn't compare yourself to the best when you're just starting in something.
Success is measured by how much fulfillment you can get out of your life, be it through your enjoyment or your goals. Simply enjoying yourself counts as being successful in my books. Search for something you enjoy, do it, and don't compare yourself to other people.