So as fans of the original games went through middle school, high school, and college or the work force, there were some that appreciated the games for their simple yet complex RPG elements, and others who couldn't get past the childish facade that the games seemed to be associated with.
Thanks to the merchandising and anime not being crammed down everyone's throat in a heavy handed manner any longer, as of 2016, the Pokemon games have become more acceptable for people of any and all age range to enjoy without being teased or harassed for their enjoyment of it. A lot more emphasis has been placed on the intricacies and competitive nature of battling; these elements have helped the series be taken much more seriously.
Going back to these original games is going to pose a bit of a problem to some fans. See, there's three types of Pokemon fans for the most part:
1) People who grew up with the original games and have stuck with the franchise ever since.
2) Gamers who came into the franchise later and never played the original releases.
3) People who were fans of the original games but grew away from them.
These re-releases may only be really appreciated by fans of the third group.
Many of us original generation of Pokemon fans didn't realize at the time just how broken Pokemon Red/Blue/Yellow are. Much has been made on the internet about the glitches and errors that have been discovered and exploited. Missing No, the Mew Glitch, the Lost City; the list goes on. Pokemon was an ambitious project of a game, and quite a few mistakes were left in the programming and coding.
There's also a glitch where your Pokemon can skip learning a move if they level up two levels at a time. Let's say for instance you have a level 5 Pokemon that learns a move at level 6; however, you earn enough experience in one fight that catapult you from level 5 to level 7. Anything you would've gained at level 6 becomes eliminated.
Going beyond coding mistakes, the games also weren't thought out from the perspective of being well-balanced in a competitive way. The Psychic type Pokemon are extremely overpowered. Unlike the games to follow, Generation 1 Pokemon titles operate off of only four statistics for the Pokemon: Attack, Defense, Speed, and Special. There is no Special Attack and Special Defense, just...Special. The end result of this is that any Pokemon that's supposed to have a great amount of Special Attack or Defense power is going to be highly rated in each. This means that a powerful attack automatically becomes a powerful defender; at least in terms of special abilities. So that would make like...all the Psychic type Pokemon fall into that category.
Psychic types are also strong against Poison types, and as it just so happens, a LOT of Pokemon are either primary Poison types, or have it as a second type, i.e. Grass/Poison, Bug/Poison, and Ghost/Poison. The latter two of those are especially important. Psychic types are supposed to be weak against Ghost and Bug moves, but the problem with this is that almost all the Bug types are partnered with Poison type, and the only THREE Ghost type Pokemon are all Ghost/Poison, making them weak against Psychic attacks.
These balancing issues go even deeper thanks to problems with the actual moves. Ghost type attacks are supposed to be "super effective" against Psychic types, but none of the Ghost type moves actually work this way. There are three official Ghost types moves in Red/Blue/Yellow: one of them is Confuse Ray (which doesn't do damage and causes confusion), another is "Night Shade" that only does as much damage as the level a Pokemon is at, and the final one is "Lick," which is a weak attack in general. So only ONE of the THREE Ghost type attacks could actually damage a Psychic type...and even then it wasn't coded properly to actually work against a Psychic type.
Bug moves were even more ridiculous in this matter. There were four Bug type moves: Leech Life, String Shot, Twineedle, and Pin Missile. All of these attacks do damage accept for String Shot, but the bigger issue is that the Pokemon that learn these moves are either not a Bug type at all, or are also part Poison type. Twineedle for example is learned by Beedrill, who is Bug/Poison: don't want to put him up against an Alakazam. Jolteon learns Pin Missile, but he's an Electric type. Paras and Parasect are the only Bug types who actually learn a damaging, Bug type move in the form of Leech Life.
Now, that third group of fans I mentioned before are probably not going to care about this so much; they're not playing the game for its competitive matchmaking metagame, they're playing it for sheer nostalgic enjoyment. As for those fans in the first two groups, those who have been with the series all along or came into it later, are going to be in for a potentially cringe-worthy surprise by returning to these games. There's a very good reason why Pokemon Red and Blue were remade for the Game Boy Advance as Pokemon Fire Red and Leaf Green; the original games were comparatively broken next to the ones that followed them.
So as the due date for the re-releases of Pokemon Red/Blue/Yellow quickly approaches, I want to caution those who are looking forward to diving back into these nostalgic classics. There's quite a bit wrong with these old games; problems that may loom too larger for nostalgia to overshadow. If these three games were all you knew growing up, then you're in for a treat; but those of us with the knowledge of what Pokemon has become, may end up looking back in disbelieving shame at the origins of a beloved franchise.