I think there are:
groudon
rayquaza
latios
regice
registeel
regirock
regice, regirock, and registeel are really hard to find, so you may want to look them up
Sadly, no. The creators of the game forgot to add in the Pokedex, so trading is impossible without GameShark. :(
Tornadus, Landorous, Reshiram, Virizion, Terrakion, Cobalion, Kyurem, and Victini.
if you want to cheat to get all legendary Pokemon on ruby you have to play on the computer
No, EX Pokmon do not count as basic Pokmon in the Pokmon Trading Card Game.
No.
you can't get the black flute in leaf green but you can in Pokemon ruby, sapphire and emerald then trade it to leaf green.
Have a ruby or another sapphire trade you a legendary!
Groudon and Rayquaza
There are 6.
Ground
The Legendary Pokemon in Ruby are Kyogre, Groudon, Rayquaza, Deoxys, Jirachi, Latios, Latias, Regice, Regirock, and Registeel.
groundon, latios, rayquaza and the three regis.