Actually Final Fantasy 7 came out in 1997 on the PlayStation, Which was where he used Omnislash and the Fire emblem game that Ike made his first Debut was Path of Radiance which was on the GameCube and from what Ike's trophy says that It came out in 2005 and the Great Ether in the original game It was a regular slash move and it belong to him, Sakurai probably added it in as a reference.