Not to put too fine a point on it, but the Borg, like Q, in my opinion became less interesting and more banal the more they were on screen.
I rather liked the idea of an enemy whose existence was totally subsumed into a hive mind. The introduction of some mega-Borg queen seemed to belittle the whole concept.
Likewise, I also felt that Q became increasingly stupid, especially in Voyager.
I'm just writing this thread to complain about two of my Star Trek pet peeves.
And I'm just writing because I agree with you. Every series has a "favorite enemy," whether it's the Daleks for Doctor Who or the Borg in TNG. The problem is: How can you have an enemy you fear after defeating it every single time? Sooner or later, that unbeatable enemy loses that fearsomeness. (Oh, look! It's the Borg AGAIN. Shall we laugh now or wait until the crew kicks hom off the starship?)
As to the Borg when it was first introduced: I really liked the idea of a race that was after only technology. It was frightening wandering through the ship and them not giving two hoots and a holler about the crew.
You also had to beat them head on since there was no lead figure you could trick by saying: "Look over there. It's Raquel Welch!" Then the lead person turns to look and you've gotten some big gun you pull out and that's that.
That was what the Borg Queen was all about. Distract her, and the rest of the crew had a fighting chance. Bah, humbug, even though I enjoyed "The Best of Both Worlds," though Picard should have died when Crusher took out his nanoprobes and no explanation given.
For the Q, he showed up and did what ever he wanted whenever he wanted. If I'd been the captain, I'd assign at least one team to come up with ways to boot him off the ship. (Maybe that's why Q never bothered Kirk and company.)