Hi, new to the forum here but as I was recently discussing this a little bit on another Trek forum thought I might commence here.
My personal take is that 'I, Borg' is quite superior to 'Descent, Parts I and II'. Micheal Piller had the right notion that after the events of 'Best of Both World's' and the general epic-ness of that show that there was very little way to 'top' it.
Unless you take it right back to a single drone.
It allowed for a much more emotional storyline with further follow-up from Picard's assimilation which hadn't been covered really since 'Family' and introduced the idea of a Borg given individuality.
The argument over the merits of genocide were pretty well covered as well before the final decision to introduce the program.
So, 'Descent' was quite well primed to then extend that and progress the story further. The problem, IMO, was the very bad decision to include Lore and a 'Federation Takeover' plot. I feel there were two separate stories worth telling - the Borg continuation and the Data/Lore story but they did not work well together as a single two-parter.
The Lore part is just too cartoonish in the end.
As for FC - I don't mind the Borg Queen. I can appreciate technically it's not 'out-the-box' thinking to devise a physical opponent for Picard to go up against - but then 'out-of-the-box' thinking is, I believe, not a comment that can often be stated about 1990s Star Trek. She has a function in the film and although it probably (along with 'Descent' marks the point at which the Borg began to lose their impact, they remained sufficiently threatening to that point.
VOY however, really and very badly eroded them into a completely unthreatening enemy who were never really a huge problem for the ship and crew.
The over-use of them in that series did destroy them.