Originally Posted by
Hibbyradge
To me genre defining means something excellent which contains all the elements of the genre.
Something you'd look to if you wanted to understand what a film genre was about.
For example, there are thousands of war films, but I'd suggest that the comparitively recent Apocalypse Now was a candidate for that genre's defining title.
Anyway, unless you can offer a specific title to usurp it, The Godfather gets the nod. (G1 definitely, probably G2 but maybe not the third.)