I voted for VII because it's the only one that's easy without having to rely on something. V may be easy if you max out the Jobs, VIII may be easy if you exploit its system, X may be easy if you use the characters properly, XII may be easy if you set up your Gambits well and so on, but VII is easy if you have eyes and can successfully push a button. It's the only FF I've played that isn't easy because of something; it's just plain easy.