gamtime: ~26hrs.
complete: 100%
after all the work of finding all the weapons in the game, the ending they "reward" you with is pretty stupid.. the ending is an extension baby ending. after the mother is engulfed in the great time that seere emits and then sent to a different time and you follow in persuit.
all the way to modern day tokyo.. the final mission is a simple game of hitting the correct buttons on the controller to repel soundwaves of the mother's screams.. after the mother is completely destroyed, you get killed by two missles of the japanese air force.. the end.
so..... i guess there was no resolve or any reason storywise to collect all 65 weapons..
i think don put it best when he said, "what were they thinking when they made this game?!"