6 is definitely one of my favorite games of all time. Of the series, definitely had the best music, and awesome characters. The bosses were total pushovers with most having around 40k health but the game itself was a landmark in that it was finally breaking away from the "excuse to just go kill a lot of monsters" that defined the genre.
7 gets a lot of hate just because its really popular, and people think its cool to hate popular things. Whatever the case, it was a solid game, and if you are expecting pulitzer prize winning stories, then video games aren't the best place to find them. Imo, most storyline bitching is kind of lame, considering how i've yet to play a game with anything close to a deep and though provoking plot.