This was an interesting Creepypasta when it first appeared, but I always thought there was better. Of course then again I've never played much Pokemon.
To be honest I'm a little surprised there hasn't been more done with video games in horror, they made an attempt a few years back called "Stay Alive" which turned out pretty bad (and stood out mostly for having Elizabeth Bathoroy as the bad guy), but otherwise it seems to be far more neglected than I'd expect with all the techno-haunting movies about video recordings, websites, found footage, EVP, etc...
The problem with the whole "Ghost Black" concept that occured to me, and also prevented it from working on it's intended level (besides not being a Pokemon player) is that the set up is bad. Even allowing for this article being written two years ago, consider that Pokemon Red is an old game, the odds of someone old enough to have played it originally being into Pokemon to buy the cart out of nostolgia, and what's more play through the entire game again seems to be pushing it a bit, especially as it would have required a very old gameboy system which the writer would have needed to have sitting around in working order. To me it always seemed like an implausible discovery, like a lot of second rate creepypasta, many of which beg the question of "if this is true, how would anyone know about it to relay the story".