about the games
Pokémon Ruby and Sapphire, the third generation in the incredibly popular franchise, were released in Japan in 2002 and the rest of the world in 2003 for the Gameboy Color. Like the second generation of games, Gold and Silver, Ruby and Sapphire take place in an entirely new region called Hoenn. Unlike Gen II, the Hoenn games were not backwards compatible with the older games, owing to various technical issues, and as such were totally separate entries in the series.
The Hoenn games introduced a wide variety of new gameplay mechanics to the series, some of which are now a cornerstone of competitive gameplay. Each Pokémon species now had its own unique ability that affected various things in battle (such as improving type affinities in battle, or offering stat boosts, and so forth). Individual Pokémon also now had one of 25 natures that increased one of its base stats at the cost of decreasing another.
Also introduced in R/S were double battles, which are 2-on-2 matches for Pokémon. A number of moves were introduced for use in double battles, and one of the gym leaders of the region is a set of twins who solely fight in a double battle.
While Berries did exist in Gen II, in Gen III they were made infinitely more accessible and furthermore given to the player to grow and tend to rather than daily gifts. This is a mechanic that's carried forward for the most part throughout the series.
Unique to the Hoenn region is an entirely separate way of competing with Pokémon: contests. In Contests, moves are used not to defeat an opponent but instead judged in five different categories (cool, tough, beauty, cute, and smart). Contest halls appear in multiple cities across the region, and there are four ranks for each category. Taking part in contests is optional, but it's a whole different game unto itself.
Also unique to Hoenn is the ability to create a Secret Base, which is literally a little secret home for yourself that you can decorate with furniture and Pokédolls. There are Secret Base spots all over Hoenn, and all that's required to get in is the move Secret Power — and the memory of where you left your Secret Base!
Finally, the R/S games included the PokéNav, which is kind of a sequel to the phone in the Gen II games. It allows you to call trainers for a rematch and has a built-in map.
Ruby and Sapphire are also notable in that their plots are actually significantly different depending on which version you play. In Ruby, Team Magma seeks to resurrect Groudon in hopes of increasing the landmass; in Sapphire, Team Aqua wants to ressurect Kyogre to get more water. They're both absolutely ridiculous, and it's one of the reasons the Hoenn games are my favorites; you can't take either team seriously no matter how adamant they are about their absurd goal. It's fantastic.
I also feel obligated to mention that this is the one game where the player character actually has a father. Of course he's still never home, but that's because he's a gym leader.
Like the two generations before it, Ruby and Sapphire were followed by a third game, Pokémon Emerald, in 2004 (2005 outside of Japan). However, as much as I love Emerald, this site doesn't cover it.
Some history first: the Gen I games were remade in the same generation as R/S as FireRed and LeafGreen. After that, the Gen II games were remade in the next generation, Gen IV, as HeartGold and SoulSilver. Given that the Pokémon franchise is at this point a huge cash cow, it was generally assumed that the Hoenn games were going to be remade eventually, it was just a question of when and how.
It finally did come true in Gen VI, with Omega Ruby and Alpha Sapphire releasing around the world in November 2014 for the Nintendo 3DS.
In general, OR/AS is very much in line with the Gen VI games, X and Y — it features all of the improvements that came with the move to the 3DS and the various changes that have come since Gen III. It's got the new Fairy-type (and all relevant Hoenn Pokémon have swapped to it); a ton of Hoenn Pokémon have new Mega Evolutions; it's got Pokémon Amie and Super Training. You can even evolve your Hoenn Pokémon into their later-gen evolutions if you want; they're all in the Hoenn dex now, and OR/AS in general is as flexible about the National Dex as X and Y were.
There are a couple of changes to the plot and some brand-new characters. Most notably, after you beat the Elite Four, there's an entirely new story to play through centered around Mossdeep Space Center, Rayquaza, and Deoxys. Given that there was a persistent rumor back in the day that the number of rocket launches had something to do with catching Deoxys in the original game (it doesn't, it just tells you how long you've been playing your game), it's pretty entertaining to see a whole storyline about it in the actual game!
There are a ton of changes between the remakes and the original games; Bulbapedia has a full list. If you've never played the original games, or if they're a big part of your childhood, I highly recommend picking up the remakes; they're absolutely fantastic. Hoenn is a really fun generation, and the remakes are even better than what I remember of the game I loved as a kid.