I dare you to show me how objectivity can be used in genuinely classifying a game as overrated. How in the world are you going to measure it?
This. That's why the word "overrated" is almost always misused. I'm not even sure you can use it and be correct in the grand scheme of things. What something is "rated" is based on a general consensus. An individual disagreeing with that consensus means nothing other than they disagree with whatever the more popular opinion is.
We're not rating stock speeds of sports cars or the atomic mass of elements on the periodic table. How good or bad a game is comes down to opinion at the end of the day. I don't like some very popular games. I love some rather unpopular games. Doesn't make any of them over or underrated.