This has to be the most pathetic fail attempt to certify a record Guinness has ever pulled... not that I'd have any idea because I haven't read Guinness for about 7 years.
/hollow statement for effect.
Where to start on how bad this method is... and the worst thing about it is that attempting to poll every gamer on the planet would probably; if anything, skew it even MORE in the direction of unobjective, ignorant and mindlessly fanboyish bias.
How fatuous is it for any individual to dare to call the greatest endings in the entirety of gaming history? let alone a 'gamer' who's only ever owned an X Box 360 and whose game rack is limited to CoD 4-MW3 and a handful of lackluster games. (which would explain The Force Unleashed II) Nostalgia being equally unreliable as it is strongly connected to the unique appreciation of having experienced something for the first time in a younger stage of life.
And despite their ignorance or dellusions; the reality of polls on games is that most individuals don't care to go so far as to even consciously attempt to judge objectively.
Consider that 'gamers' are a notoriously immature, unsophisticated, biased and petulant collective to survey.
Never mind that even with the right intent, the matter of what methodologies one would use to identify 'greatest' and the appropraitely desired definition of the word itself is so subjective.
For a popular survey on something so subjective as this; the best you could do is a relatively small sample of extremely well-educated media and literature critics and expose them to every game (worth playing) ever made; while ensuring they had vast experiences of other media as sources for comparison, so they weren't under illusions about originality or sophistication. Accepting results only should controversy be minimal.
How big a priority are plot sophistication, unexpected twists, allegory, presentation, emotional congruence, originality, or simplicity and finality relative to each other in the measuring of 'greatness'?
Terrible. Just awful.