Is it fair to criticise a game for being too hard/easy?

[VAMatt]

Flilix said:

-Are they both equally fair for me to say?
-Are they both equally fair for a reviewer to say?
-Would it be fair if a reviewer lowered his score because of these complaints?

You can say anything you want, and it is fair.  It is your opinion.

As for a professional reviewer, I'd say that it is fine for him to score the game based on difficulty, so long as he tells the reader why he scored it the way he did.