Hi,
When it comes to "featured" product, you will be able to show only "parent" products, it is easy. Basically you will "unchecked" the "Featured" option for "child products".
But when it comes to "recent" and "top10" product groups, then there is no way to skip child products. Since they act like a standalone product as well, they appear as they are regular products. If you disable our VM Template, you will see it is also same in the official Virtuemart as well.
I believe VM Developer has designed it that way, and it makes sense. For instance, you have T-Shirt "parent" product and have "Red, white and brown" child products, and the RED is best selling products, you might want to show RED child product in the top10 products group only, Instead of Tshirt parent product.
If you are asking a solution about it, i don't have it. It would probably require little CORE hacking, and we don't recommend this kind of edits since eventually you will lose them once you upgrade your Virtuemart.
Cheers.