The correct word for the seven films is 'Heptalogy' ranging from 2004 to 2010.
Trilogy means three, for example:
Tricycle - 3 wheeled bicycle -bicycle meaning two wheels
Tripod - 3 legs
Triangle - 3 sided shape
Trilogy - a 3 part series (film, book etc leading into Quadrilogy (four))
Triple - Multiples of 3 (3,6,9,12 and so on)