In Critique of Judgement, Kant analyzes the beauty of art as well as how genius creates art. In his view, art should be beautiful, and beauty cannot be created through merely applying rules and skills learned. However, art should also stand as a perfect model, giving us a "standard or rule by which to judge" the beauty of the art (§46, 308 as cited in "Kant's Aesthetics and Teleology: 2.6 Art, Genius and Aesthetic Ideas"). Hence, his argument is paradoxical in saying that art should not follow rules but should provide rules. He reconciles this paradox by arguing that genius enables an artist to produce works that can be judged as beautiful without the artist needing to follow any set rules in creating the piece. As a genius, the artist has the ability to rise above nature and nature's set rules and create his/her own rules by which others can use to judge the art. It's also important to note that Kant sees the genius artist as being unable to really explain the means by which he/she created the beautiful artwork, the same artwork that would set new rules and standards through the creation. In other words, the artist sets rules and standards through his creations without really being able to explain his/her method or really what those rules and standards are. The artist's ability to create art will be so innate that he/she will not be consciously aware of the process.
One con concerning Kant's definition of genius is that the definition is a bit limiting. For example, according to Kant, Newton would not be classified as a genius because he clearly demonstrates all of the steps he used to reach his conclusions in his proofs in the Principia. Hence, according to Kant, genius is something beyond just brilliant intellect ("Kant's Aesthetics and Teleology: 2.6 Art, Genius and Aesthetic Ideas"). It's also important to note that Kant sees aesthetic beauty, or art, as being the exact opposite of rational ideas because rational ideas cannot stem from imagination. Hence, Kant separates intellectual abilities, like Newton's abilities, from aesthetic genius.
One pro concerning Kant's definition of genius is that it clearly defines the process through which one creates art through the imagination in such a sublime way that it both exceeds the rules of nature and sets its own rules.
Kant defines genius as being able to come to conclusions and having knowledge of a subject without having to be taught or told, as most people would. One pro with Kant's theory is that it makes sense, and it doesn't contradict any previous works of his. Basically, he's consistent with his definition of genius.