"A) what do you mean by "best"
B) what do you mean by "engineer"?"
Dictionary definitions should suffice.
Allow me to rephrase:
A) By what metric are you comparing "engineers" by which to be able to rank them against each other?
B) What fields of study do you consider to encompase "engineering"? Should it cover only fields that require certification as an engineer, or are you using the less rigorous version of the term that essentially means "person who makes things"?
So no, dictionary definitions most definitely won't suffice.
A) It's open ended, but you can use influence, industriousness, inventiveness or any metrics you wish.
B) Less rigorous