Solid role-playing that doesn't bore or impress.
The storyline is your standard Pokemon fare. You're a Pokemon trainer who is on a quest to defeat each of the gym leaders and make it to the Elite Four. On your way you will battle your rival, catch Pokemon, and try to stop the evil deeds of Team Magma/Aqua.
The graphics aren't impressive, but they still look nice and are up to par with the GBA was capable of doing. There is plenty of visual variety, and the scenery is very colorful. The soundtrack is fairly good as well. Battle tunes are catchy, but the standard battle theme will eventually drive you crazy after your empteenth random encounter.
Your time in this game will be spent catching Pokemon, battling, exploring, and a doing a few sidequests on the side. A lot of the sidequests are completely optional, and they consist of things such as entering contests and catching optional legendary Pokemon. The contests are relatively fun and require a surprising amount of strategy. Catching the optional legendary Pokemon is no walk in the park either. Some of them are so difficult to get, in fact, that you might actually have to look up instructions on the internet in order to find a way to obtain them.
Battling is, once again, your standard Pokemon fare. It's turn-based, but it requires a bit of strategy. Making sure that you know the types of the Pokemon you're battling is imperative because you need to know their weakness in order to take them out as quickly as possible. Gym battles are among the most challenging parts of the game, and you have to make sure your party of Pokemon is evened out properly and has sufficient attacks. If your party is inadequate, then you're going to have difficulty beating the gym leaders. Once you figure out the weaknesses of the Pokemon, battles become easy because you can spam attacks and whipe out enemies quickly. This isn't the case for all battles, though, because the people you battle will occasionally have a variety of Pokemon, but that doesn't happen all that often. Standard battles can get quite repititive after a while because Pokemon trainers tend to have Pokemon that are identical to the ones owned by other trainers in a certain area, and some trainers own more than one of the same Pokemon. The random encounter rate while exploring certain areas is also moderately high, so you can expect to get tired of battling after a while.
Exploration is somewhat linear, but it's completely forgivable becuase it's not what Pokemon games are all about. It's still fun, though, and there a lot of fun locations that you'll be visiting throughout the duration of your quest. The towns are the best part of exploration, and taking a stroll through the cities and conversing with locals is always fun.
Overall, Pokemon Ruby/Sapphire/Emerald is a very solid, lengthy, and addictive RPG that may not impress you in any way, but it's still a very fun experience that all Pokemon fans should play. If you're new to the Pokemon series, this isn't a bad place to start. This was my first Pokemon game, and it's still my favorite.