In the original English version of Pokemon Red/Blue, you can give your character a custom name, or go with preset names Red, Ash, or Jack. It may seem like a small thing, but to Pokemon super-fans, these names represent a huge divide, particularly when it comes to Ash and Red. To many, Ash is the character from the Pokemon anime who symbolizes a watered-down, goodie-goodie, "pandering to the lowest common denominator" side of Pokemon. They see Red as a completely different person, only known to those that follow the manga and the games, symbolizing the colder, more serious, mainstream-rejecting "hardcore" side of the Pokemon experience.
In short, Red is the hipster version of Ash -- so whatever you do, don't mix them up in public. That's part of why the official name for the "Ash/Red/Jack" character in Teenage Pokemon is just "Trainer." We didn't want to buy into all that Pokemon fan class distinction weirdness.
Thankfully for diehard Red supporters, Nintendo will be embracing that weirdness in just a few months. Starting on October 2nd, they'll be rolling out an all new anime that retells the story of Pokemon Red/Blue, staring Red and his rival Blue (as opposed to Ash and Gary), featuring character designs that are more loyal to the games. It's currently unknown if this is the start of a new series or is just a one-off special, but you can bet if Red gets his own show, it won't be long before people start hating on him while claiming that Jack is the best that ever was.