There's a lot more to creating a good image than just the software package you use.

Lighting and camera settings can make a big difference. Sometimes the merchant will include those in the product. If not, try downloading some of the free light sets at RDNA.

Render settings also make a big difference, but there are no "perfect" settings. It depends on the image, and the effect you are trying to get.

You might try posting one of your images here. Tell us what you don't like about it, and some of the experts here can probably tell you how to fix it.