Can people be compared across eras?

Have been busy lately. Need to find the right balance between office and home. Anyways, something that I have been thinking lately is this: can people be compared across eras?
Arguably yes. Probably no. Is it fair to compare Bradman and Sobers with Sachin and Lara in cricket? How would Rod Laver, Sampras, and Federer have played if they had competed at the same time with similar racquets and on a single surface? Heres something really interesting. Would Einstein have devised the relativity theory in the 16th century? Or could Newton have decrypted the heavens and gravity in an earlier age? Each of these individuals has been great in their respective fields. No question. I think the argument is how much of their greatness can be attributed to the tools, technologies, and circumstances of their times? Would it be even fair to do so? How can people judge the relevance and importance of the situations in which people lived in another age?

One last thought tonight. Am I implicitly trying to compare the success of people across ages? If so, then is there any measure to weigh success and its footprint across ages?