If they weren't the first games to be released, Pokémon would be a lot more different than it is now, I imagine. Pokémon that were released in games such as Red and Blue set some sort of standard on how they should be, design-wise, so in terms of that, they would either resemble monsters more, or animals, all depending on whatever titles get made first other than these two (if that makes sense). Same could be applied to them stats-wise.
As for me--if it weren't Red, Blue, or Green, I'd personally prefer it to be Ruby, Sapphire, and Emerald. I'm kind of biased on this, as these are my most favorite games of all-time; though, they do have many things that would appeal among thousands of fans, with few being locations. Most of their towns, cities, and routes are pretty distinct from each other, and when exploring, you'd always be getting some new feel and experience.
