>Gen 4 - Giratina has an alt form featured on the 3rd version of the game
>Gen 5 - Kyurem has an alt form featured on the 3rd version of the game
>Gen 6 - Zygarde has an alt form, no 3rd version but is the trio leader

So what was the plan?
Did they intentionally make the original forms unattractive so they could reveal the alt forms to drum up hype for 3rd versions of the games?
OR
Were the original forms not well received so they had to create alt forms to drum up hype for the 3rd versions?