You may have a real interest in becoming an artist and making money off of it but never had the necessary talent, but quality graphic design schools can teach you everything you need to know. You don't have to be a master painter or someone who is always working on a new sculpture or sketching out amazing portraits to be an artist; all you need is a set of finely tuned skills that you can put to work when you create new projects. Some folks go off to art school because they like art and really want to learn how to create it, while others enjoy the thought of turning art into a career, and getting an art degree is surely a great way to go about it.
Before you decide to enroll yourself into a local school, you might want to consider the styles of art that interest you the most and how those styles would actually apply in the job market. If the extent of your art interests lies with painting rocks and gluing funny eyes on them, you may not have much luck turning that into a career, but if you have a thing for creating sharp, colorful designs, you may be able to find a place in advertising, illustrating magazine ads or creating company logos.
In the world of graphic arts, almost any art style that you are at least somewhat interested in can be developed into a career level ability that will have you working the kind of job you've always hoped for, like going from sketching futuristic cars to actually doing concept designs for a living. You could have fun drawing out the kinds of characters that you see in video games and actually turn that into a career where you get to do the 3D character models for those same kinds of games.
You may not actually have a talent or natural interest in art at all and simply think graphic art and design could be turned into a satisfying career, and you would still do well to find a good art school and enroll. And whether you have a knack for creating great artwork or not, the school will be able to show you every single stroke and technique you need to know to be able to make some great artwork.
Since art school is all about providing you with the special skills you need in order to become an accomplished artist, there's no need for you to have preexisting talents. Start looking for some quality graphic design schools and get the ball rolling towards your new amazing career.