Nowadays, most of the high-ranked universities are from the developed countries. However, there are many talents in the developing countries who cannot afford such universities for their graduation due to lack of fund or other limitations. There are many examples, where these researchers from developing countries have shown their talents in some stage of their life (in their home country or abroad). Although they have graduated from low-ranked universities, their clear vision, high motivation towards quality research, and hard work make them valuable for the whole world. I don't want to mention any particular name here.
On the contrary, some of the graduates from high-ranked universities cannot prove themselves in their research life. Then what is the key issue to become a good researcher?