Pokémon Green Version was Japan's Blue Version, as they were originally blessed with Red and Green.
Then the games shipped overseas to America as Red and Blue, and Blue was then released in Japan.
Green was identical to Blue in every way, the only difference was that the Pokéon sprites were, to be blunt, abysmal.
We won't get Green because we don't need it, we have Blue, and having two identical games is not necessary.
Anyways, if you want a game with Venusaur on the cover, as you stated, there is LeafGreen now.