I am blatantly copying Carlmundo’s (and possibly others) system as I don’t care much about getting all achievements in games. If I really want to go the extra mile to find extra’s apart from the main story line, I will, regardless of achievements.

So completed means finished the main story line and beaten means either there is no end to it, or I played enough of the game for my enjoyment, or it’s a (mostly) multiplayer game that I have played to my hearts content.
The main difference between “won’t play” and “beaten” in regard to games I haven’t finished is whether I enjoyed the game or not.
Dead multiplayer only games automatically fall in the “won’t play” category.

Also, damn, this categorisation in itself already requires some dedication. :D

Finally got everything out of ‘uncategorised’ after a full day of checking… Still gotta filter a bit the ‘unplayed’ games… But that’s for another time.