It has wireless connection and you can run into other region's Pokemon and you can't do either in Ruby or Sapphire.
i think that in pokemon Emerald there are a lot of rare/special pokemon. Also i also think that in pokemon Emerald you can get kyogre and Groudon but, in pokemon ruby only groudon and in pokemon sapphire only kyogre. i hoped this helped and i'm sorry if i gave wrong information.
its a shiny Pokemon
GAME SHARK!!!!!!!!!!!!!!!!!!
you can't get jirachi in emerald, only by Nintendo events, they give out special items that helps you get rare Pokemon.
Deoxys is a legendary Pokemon and cannot breed in Pokemon Emerald. This Pokemon can only be obtained through trade and special Live Nintendo events.
Only you can get it from the preordered special disc of Pokemon colosseum.
Cressilia is a 4th generation Pokemon so you can't catch it in Pokemon Emerald.
Special event in 2004 for ruby, sapphire, and emerald
Pokemon Emerald Enhanced is a hack of Pokemon emerald. The most special thing about it is that all Pokemon are available somewhere in the game. No trading or gamesharking is necessary. Toward this end, a few new areas have been added as well. As a final note, the three starter Pokemon for this hack are Zapdos, Articuno, and Moltres.
you can only get it with a special event or game shark
Gardevoir. It has very high special attack.
aipom's evole is a Pokemon from the next generation after emerald so its impossible to receive him.