I hate to partake in a conversation like this but...
I'm sorry, what? What is so criminal about the possibility of a fan model being better than the official? It can be done with enough work put it into it. For example: Project M's Ocarina of Time Link, that is the best model of OoT Link I've ever seen, even better than the 3ds and Melee models. Are they "Mole Convention 2014" for accomplishing such a task? Are you that [censored]ing dense?
There's nothing wrong with a fan-made model being of higher quality than those used in a video game, especially if the game is on system that uses relatively low amounts of polygons. The Link example you give is true, because the original models are on the Nintendo 64 and GameCube, and the model in Ocarina of Time 3D is somewhere in between those in terms of quality.
It's also conceivable that a fan-made model could be more accurate to a video game's official artwork than a game model, especially if the game uses stylized character models or, again, low amounts of polygons. The overworld character models in X/Y have rather large heads compared to the official artwork. However, the official Yveltal model has none of these attributes. The model has more polygons than in any other previous Pokemon game, and was made by professional 3D modelers based on drawings by the official Pokemon designers themselves.
The main problem here is that the model is
not more accurate than the official model. (No offense to the modeler, of course.) I pay attention to small details on things, and there are a number of points where the fan-made model deviate from the official design. To name a few: the legs bend the wrong way, the pointed marks at the base of each finger are missing, the nose is not pointed enough, and the hair is very wavy whereas the artwork has little waviness to it. I could go on, but I think you get the point. Besides the design inaccuracies, the texture is noticeably lower in resolution than the official model.
Is the fanmade model better in quality? Just on a technical level, no it is not. Is the model more accurate? No, it is not. Is the model bad? No, it's still decent and is possibly one of the best fan-made Yveltal models out there. Is it bad that someone likes the model better than the official model? No, it's just their opinion. Is it bad that someone thinks that the design is more accurate than the official model? Not really, though anyone who does might need to pay closer attention to details.
The other part of the problem is that a number of people here seem to lack manners when it comes to addressing others, but that is beside the point.