I prefer rating each game individually than making a scale.
Example, Lego games can be very time consuming to get the platinum, but they are never hard at all, mostly because when you get 100% game completion you already have 80% of the trophies and all that is left very basic stuff (like in Lego Marvel, you get a trophy for turning Mr. Fantastic into a cup (or was it a teapot?), something you never have to do to complete the game).
White Night for me was on the hard side, not because of the difficulty, but because if you missed something you were forced to restart the whole game to get it. It took me 7 playthroughs to find all the collectibles.