The orginal DS has the capability to play GBC games so that immedaitly makes it the best for a pokemon gamer. But it does come with a huge downside which is no blacklit screen. For that reason the DS lite is preferred.
Any other options are not good because they can't play GBA games and only offer better quality which isn't that improtant.
Any other options are not good because they can't play GBA games and only offer better quality which isn't that improtant.