It's not cheating unless someone dishonestly claims that they did create a painting. Media are a means towards an end, including digital media and tools. Used well, filters which simulate conventional media can enhance anything from one's 3D render to a snapshot of the family cat. To assume that the use of the tools at one's disposal is "cheating" is too assume too much, at least in lieu of context, which in this case wasn't provided. Professional who use Photoshop for print and Web media frequently employ simulations of "natural" media for illustrative effect. It's not cheating any more than, say, the use of a live model or optical device is "cheating" in painting. Or for that matter, a photograph for reference when drawing or painting, which is in many cases a wise thing to do. Finally, there's the obvious fact that not all accomplished Photoshop users can paint, which is no reason not to try simulating a painting-like effect using the digital palette.