2D for me are definitely harder. I can't even find the second dungeon in LoZ (sad, I know), and I can't beat the second dungeon in AoL. (Also sad, I know.) ALttP I think was made a bit easier or at least appears that way. However, I think LA and the Oracle games are considerably easier than the earlier 2D Zelda games. For me, 3D Zelda games are much easier.