It’s like Pitch Black released since 2004 as The Chronicles of Riddick: Pitch Black (though the third entry is only Riddick…). As for SW, they are now all marketed without the number, even the PT, which are largely known with their number : http://www.amazon.com/Star-Wars-Phantom-Limited-Blu-ray/dp/B013JAFTS0/ref=sr_1_2?ie=UTF8&qid=1460531820&sr=8-2
Another example: the first sequel of Die Hard is known as Die Hard 2: Die Harder (video release, soundtrack albums…), but “Die Harder” is the tagline put on posters, in the opening credit it is only displayed Die Hard 2.
But again, this is how they want to sale the movies, not their actual names. So, my question was and still is: where can we find the information of the real title of a movie ? Is it written someone in the end credits along with the exploitation visa ?