Time helped me appreciate that for the excellence that it was, and made me realize it is indeed the best cliffhanger ever.
I would have to respectfully disagree with you (providing you were serious in the first place). What makes a good cliffhanger is that the ending is unexpected, but at the same time has something to do with the story being told. Look at the cliffhangers for "Best of Both Worlds Pt. I" and "Redemption Pt. I." In both instances, the whole story is being built up for the appearance of Locutus and Sela, respectively. In "Zero Hour," the story is basically concluded, and then all of a sudden some alien space Nazi appears out of nowhere (and no segue at all that all of a sudden, now we're in the past), has nothing to do with the story we've just seen, and basically only exists to awkwardly conclude the TCW thing that nobody really cared about anyway. I mean, c'mon! If they really felt that they had to give the TCW silliness some kind of closure, why didn't they just reveal who FutureGuy was? How about making him a Romulan who's trying to prevent Earth from winning the Earth-Romulan war that would have been a major factor in the series if it had been allowed to continue? Why space Nazis?