Final Fantasies II, III, IV, V, VI, VII, VIII, IX, X, X-2, XI, XII, and XIII have you no right to call themselves Final Fantasy, because they have nothing to do with the original game, or with each other.
Guitar Hero 5 has no right to call itself 5 because there were never Guitar Heroes 1-4, or even an IV.
Halo 3: ODST has no right to exist because Bungie specifically stated Halo 3 would be the last one.
Assassin's Creed II, Dead Rising 2, and Half-Life 2: Episode Three have no right to exist because the original was fucking terrible.