Well just becoz noone owns the game doesnt make it tough(percentage) and the fact that some games need 250+hours of gameplay neither! Most of the games r piss easy honestly,..it just takes forever but they r still easy! the list is disproportional and some games r ridiculous,.. and really tough games r not even listed!
Proved Examples:
Resistance 2: finish the game on easy,go to chapterselect and finish last checkpoint on Superhuman,done,...online takes a while but it`s piss easy (done legit)
Singstar: install Soundgeneratorsoftware by Timo Esser + Frequency calculator by sengspielaudio,..done, online takes a while but again piss easy and legit ,...well kind of with a little help (done legit with the help of the mentioned programms)
GTA IV: it doesnt make sense in this list at all (done legit)
AvP and Co

Those 2 games r ancient and thats the point, learn the level by rote,...done, the enemies r at the xcact same spot every single time ,when u have died three times u know where they spawn (done legit)
Far Cry 2: Really really easy,just a bit time consuming! thx to ingame glichtes no biggy! (done legit)
OP: Flashpoint: another piss easy 1 due to a familiar trick, play story on easy and save the game at the last checkpoint of level 9 and put it on an usb or whatever,finish the game and reload the save, before hitting "continue story" change difficulty to HARD,finish last checkpoint done! (done legit without the trick)
Bulletstorm: Really? I did Bulletstorm couple of days ago and there is nothing even close to tough not even challenging!
Naughty Bear: Same, its a fairly average sneeknpeek! U put that in the list u have to put all Splinter Cells and MGS in here,and they r way tougher! (72% but cant be a...d atm)^^
Ghostbusters: Now it`s gettin awkward, no further comment! (done legit) PS: the fact that the servers shut down makes it unobtainable but it wasnt tough)
REALLY TOUGH SHIT: TC: Razing Storm,nail`d,Mod Nation Racer,Binary Domain,Inversion,Max Payne, Capcom vs Marvel(all of them),Lord of Apocalypse,Disgaea(all of them),White Knight Chronicles 1 (made me mad, if u dont get the drops u dont get the binds,no binds no gear,no gear no drops! vicious circle)
My Opinion!Greetz