I see where you're going with the positives and negatives bit, but that system seems a bit too simple to differentiate and rank a list of 100 games. A system like that can be used to eliminate games from contention, but I think the ultimate problem will be how to actually RANK the top 100 games in rightful order. A system of positives and negatives is not specific enough to show a discernable difference between, say, #7 and #8. The reason I wanted to use a rubric system was that it's ultimately based on math, which makes it much easier to ascertain final rankings. I also think you're underestimating the potential of a universal rubric, because combining it with a weighting system could help all games have a chance, provided the distribution of weight is universally acceptable to us. I envisioned a weighting system that allowed us, as the users, to emphasize the "non-negotiables" that we feel every great game must have. Sure there are some great games that lack a deep story, but a proper weighting system would allow that game to compete if it excelled in other areas. This is why having many categories to rate a game is so important, so a game lacking in one area can make up ground in the other areas. The trick, then, becomes actually striking the correct balance of weight and categories, which of course would be long and strenuous. I still think it's possible though, and believe it's the best way to go.
Ultimately, even the definition of a "great" game is subjective, but I think we're intelligent enough human beings to come to SOMEWHAT of a consensus on what that is. If we can at least agree on that, we have the potential to create a rating system that accurately evaluates each game and gives it a tangible score. My hope is that in the end we can end up with something like the NFL QB rating system: Not everyone agrees with it, but it's generally accepted and the most accurate method available.
Hell, I'll be happy as long as we can come up with something that is even modestly better than G4 and other lists. I don't care if it's perfect.