Well,actually I think that Pkemon Emerald is the best,because you can catch both Groudon and Kyogre(this is 100% true) and there is a Battle Frontier.
Currently, Jirachi is not obtainable through traditional methods in Pokemon Ruby Version.
the cheat is A3AFC93BCAE30FEC for CELEBI
It's not possible to get jirachi unless you get it from the special disc of Pokemon colosseum.
You can't catch Zekrom in Ruby version.
You can't catch a sentret in Ruby version, but you can catch one in Emerald version.
You cannot catch Ponyta in Ruby version, nor Sapphire version. You much catch it in Fire Red or Leaf Green and then trade it to Ruby or Sapphire.
ruby, sapphire, emerald, fire red, leaf green
jirachi is on the first route but is very rare i dont know the others though.
You can catch Groudon,Rayquaza,Latios,Deoxys,Celebi,Jirachi,regiice,regirock,registeel,and Mew
Jirachi cannot be caught in Pokemon Diamond. It can, however, be transferred from Ruby, Sapphire, or Emerald, assuming you got it from a Nintendo event.
You cannot catch Mew, Celebi or Mew in any Pokémon games however you would have been able to get Jirachi provided you had pre-ordered Pokémon Colosseum and received the pre-order bonus disc which would have allowed you to download Jirachi to either Pokémon Ruby or Pokémon Sapphire. Jirachi can also be obtained from early version of Pokemon Channel for the Gamecube upon completion of the main story.