wats the difference between ruby, sappgire or emerald

out of those, i think those are the only real pokemon games on the gba( excluding firered and leafgreen) which ones are better and do you think that there worth buying if i have fire red and will be getting diamond

Pokemon Ruby and Sapphire are basically the same, besides Pokemon and small plot changes. Basically, in Ruby, you have to stop Team Magma from doing its evil deeds, and in Sapphire, you need to stop Team Magma.

Emerald takes the two stories, mixxes them together, and gives you more content then Ruby or Sapphire. Emerald has more Pokemon in it, including some not available in other GBA games (Sudowoodo, for example). It adds a few new features, like Pokemon doing little animations when entering battle (they arent too good though). After the Elite 4, the Battle Frontier opens up, which adds tons of new content. Emerald is the best of these three if you never played on. Unless your a huge Pokemon fan, you might not wanna buy this is you have Ruby or Sapphire.