Cuz Substance is a fairly new version and they would release it as a totally seperate game so they could get more money if it came to NGC
But someone posted this in the other topic.. aaaaand I doubt it's true... the only place saying that it's both a remake of MGS1 AND a port of MGS2 is this one site... IGN and videogames.com only say it's a remake... *shrugs* I think it's just a remake...