3DS Max is considered to be the... "standard," I guess you could say. Everything about model importing was tailored to work with 3DS Max (though other Autodesk products like Maya work as well). I don't know anything about Cinema 4D but if it's anything like Blender, the DAE exporter might be just slightly off, which might lead to weird things like sticking into the ground.
I can't say for certain but I think Cinema 4D may be the issue here. The textures and eyes and stuff can be fixed by editing materials and such, but you might want to give 3DS Max a shot.
I think I figured out exactly why his face looks off to me. It looks too flat.
Also I think it would have been a good idea to move Marth's cape bones and rig his coat tail to them instead of just rigging to the legs. It would look more natural.
Nonono, I'm not saying it's bad, I'm just saying the model itself looks really good. If that makes sense.
The render itself is top-notch quality, you can clearly see that in the reflective detail added to it. That's waaaaaaay above and beyond what most people would settle for these days.
I think the main issue is that his eyes are really small, and there are no shadows to add depth to them on the texture.
This and a couple of other things. Namely,
-The eyebrows are a bit too thin and a bit too arched -The hair kind of looks like it's melting on the left side, it should fan out a bit more -The nose looks like it might be a bit too wide, hard to judge -His eyes aren't exactly crossed, but they do look to be a bit too close together -The mouth doesn't seem wide enough -His head generally seems a bit small compared to the rest of his body
That's all I can really tell right now. It's hard to put this stuff to words. :|
Though I think you got the general shape of his face correct. As you said, it'll probably look better with transparency added to the hair.