Some would wish to define an artist based upon how many media in which an individual was proficient or how many years he or she invested in honing their skills. To me those are irrelevant factors. There are those who know they are (or are destined to be) artists from a young age and their lack of years does not disqualify them. There are those too poor to afford sophisticated equipment and expensive materials and that does not prevent them from making art. I've made some of my best pieces with a cheap ballpoint pen (the kind you can buy a bag of at Walmart for about $3.00).
There is much more to being an artist than simply being able accurately reproduce an image, whether from a photo or from life. If that were the case then cameras and Xerox machines in and of themselves would be artists. Sadly most people seem to gauge artistic ability or virtue by how "realistic" a piece of art happens to be, however I've seen many realistic images which clearly display technical prowess yet completely lack the soulful aspect which I think is definitive to art — they were simply pretty pictures. On the other hand I've encountered work which shone with inspiration and yet the technical ability of the artist may have been somewhat lacking. Personally, I prefer the work which shows a real connection with the subject or idea and a less developed skill level to those works which flaunt realism without depth. Rendering is a skill, a useful and worthy one, but it is nothing without heart, soul, and inspiration. Skill can be taught and acquired, inspiration cannot. While experience and skill in reproducing the work of others is valuable, all of the training in the world with the most expensive materials will not make you a true artist — if your work lacks soul it's just a gratuitous display of your technical proficiency, nothing more.
Personally I believe that the best artists are those that have a great balance of both skill and soul. Skill gives you the dexterity and vocabulary to express your visions with clarity and precision, but without soul you have no real vision to express. Soul gives a purpose to your skills.
A man who uses his hands is a laborer.
One who uses his hands and mind is a craftsman.
He who uses his hands, and his mind, and his heart is an artist.
- St. Francis