Alright, put it to you this way.
If Ash and red aren't the same person, explain how they both know Professor oak, all the gym leaders that have the same names (or were they born from their mothers with the same name?), Both know a mean son of a rival, Both live in a world where exactly the same types of animals come out and they use exactly the same type of items to catch them, and indeed that the culture of such is the same in both worlds, that they both go to cities that have the same names, such as Vermillion city, Cerulean city, Pewter city, Veridian city, Cinnabar island, Fuschia city, Saffron City, and so on, both meet a pokemon expert known as Bill, both have similar clothing (at least from what you can tell of the 8-bit image, such as the hat and such), both win badges that look exactly the same and are called exactly the same, both go to a place called the SAFARI ZONE, both go through certain places that inhibit certain pokemon, in which those places correspond (for instance, they both travel to veridian forest, and in both they meet bug pokemon), both seem around the same age, both meet a bunch of people known as Team Rocket, and their leader, Giovanni, as the 8th gym leader, both meet Brock and Misty (both of which have the same pokemon in the anime as they do in the games), both go through mt. moon, etc etc.
And also if you listen to Ash throughout the series at all you'll know he wants to become the greatest pokemon master of all time, which entails becoming champion. Why else would he be collecting gym badges? To catch pokemon? that don't make sense to meeeee.
Now i will comprimise and accept that Ash can be an other of red, for the sake of it, but I don't think i can accept they are two completely different people, for the reason above, the big reason: the differences are so small, and the similarities are too huge.