I personally think, just from what I can tell, that all the new people are genuine. Probably all just lurkers. These forum games are oddly fun, and once the ball got rolling for Nintendo, it brought out all the Nintendo lurkers. That's my theory. It's just too much effort to try to get friends to help, and too risky to make an alt for a stupid game, so I don't buy either of those explanations. It's certainly surprising how it all turned out though. That said, a post count limit would be completely fair. Thanks to the non-Nintendo fans for being such good sports.
Sound of Rain, do you think a few of these games limited to one first party would be a good idea? I'll be honest, I just love Nintendo as a game developer. Having five Nintendo games in here would be like having five Square Enix games. If you like a developer's style, you'll like a lot of their games. Nintendo has an advantage here, and to some degree, Sony, while Microsoft gets it the worst. Having a separate Nintendo, Sony, Microsoft, and 3rd part elimination game would be a lot more fun for everyone. It would allow for more variety, and eliminate brand bias. Quite frankly, I adore a lot of Sony franchises, just none of the ones you listed aside from maybe LBP, so I'd like to see a Sony specific one with series we haven't seen since the PS1/PS2 eras. And don't get me started on 3rd party. You just can't summarize all that 3rd party has to offer with just 5 games.