Conventional 3D used in today's 3D games uses triangles to create an object or person and just imposes a texture on triangle based objects. The main problem here is that the result is a 3D object which looks more like a collection of geometric blocks than the realistic and lifelike object the creators wanted. We get just a approximation or object and creatures true form. In today's film industry, almost anything is possible. Just take a look at the type of animated films that companies like Pixar do and you will be truly amazed.
Films uses a technique called higher order surfaces or curved surfaces.
One question remains. There are a few answers to that and the first is that all 3D rendering engines used in today's games are still based on triangles. Answer is pretty obvious - because we didn't have any alternative at least until now. The second big issue is that if we use fancy techniques like curved surfaces we will break compatibility with older chips. Always keep in mind that programmers make games for lot of computers and cards from the low end to the high end.