I think Voyager totally pooched the Borg, then again I think Voyager is by far the worst of the shows so screwing the Borg is par for the course.
I've even come to appreciate Enterprise a lot more after re-watching it start to finish on DVD (S1 ok, S2 terrible, S3 good, S4 great). I'll be giving Voyager the same chance later this year but I have already seen a lot more of it than I had of Enterprise before re-watching it so I'm not expecting Janeway & Lackeys to get the same reprieve in my eyes that Archer & Co. got.
P.S. Yes, the Borg were meant to be the big, bad, super scary, overwhelming and unbeatable opponent when they were introduced in TNG.