Well, there is a whole new third generation of pokemon, plus some from the past two generations. There is also the safari where you can catch a whole bunch of 1st and 2nd gen pokemon.
latios and latias appear in random patches of grass and areas of water after you catch Rayquaza or make him faint.(after saving the world in Sootopolis.)
No you cannot catch Celebi in Pokemon Emerald.
No I don't believe you can catch a ledyba in emerald
No, EX Pokmon do not count as basic Pokmon in the Pokmon Trading Card Game.
You can onl catch LUNATONE in SAPPHIRE but you can catch solrock in emerald
yes you can catch a Manaphy on emerald. (if you have a game shark)
Yes, You can catch Groudon in Pokemon Emerald.
You can't catch one in Pokemon Emerald.
You can't catch it in Emerald. T-T
you can not catch it
Its not avalible in emerald
tentacool and magikarp ... As you can also catch goldeen on emerald