One of a kind to be sure, for now anyway. But here's the scoop.

It's the difference between a linear world game and a sandbox game. The Call of Duty saga is a linear based shooter. The Far Cry games are all Open world, except for the very first one. So ifMortal Kombator Street Fighter is a, "closed stage fighter," Super Smash Brothers would be classified as an, "open stage fighter." CSF vs OSF. And don't mention Streets of Rage. Streets of Rage is purely a beat'em'up.