Cause the story the characters it all makes you hunger for more. Even now it has the best storyline of any game I have played. It just throws you into a world with characters you immediatly fall in love with. Its villians have not been surpased yet in an FF. Im sorry but seymour and Vayne are clones and still choir boys compared to Sephiroth. And I couldnt bring myself to hate Sephiroth or any villian from the FFVII series. Its espcially apparent in deepground in DOC that they arent BAD its just the only thing they know. The same can be loosly said about Sephiroth. All in all it just captures you in a world unsurpassed by a game or movie yet.