It depends. Diamond has better graphics, but Emerald has a better plot line and in my opinion is better.
You can't get them in Pokemon diamond, you must trade from Pokemon emerald.
You have to migrate the Pokemon from emerald.
No you Can't
no
You cannot get Rhyperior in Pokemon emerald as he is only in Pokemon diamond and pearl.
Emerald's better.
You can get Poochyena into your Pokemon Diamond by migrating it from a Sapphire, Ruby, or Emerald Pokemon game.
because it's to old and besides there are better games out there in the world like Pokemon diamond and pearl
emerald no doubt
you have to trade it from a different game, trying ctahing it on Pokemon emerald and migrate it to Pokemon diamond
I personally like Emerald better, but Pearl has better graphics.
You cannot find an infernape in Pokemon emerald for that Pokemon you need Pokemon platinum, pearl or diamond.