Some people will say that a tv show is a tv show; so long as it entertains, anything proceeding it is irrelevant. Sometimes I wish I was able to think that way too, but I too can't stand it when the 'history' of the show, or at least the history as I perceived it from watching Star Trek episodes, becomes distorted.
I have never watched a full episode of Enterprise. Some will probably say, "you're loss". Well, not really, I just can't find any joy in watching it. Maybe the stories are interesting. Unfortunately, I'm the kind of guy who likes continuity. I know that all television show continuities are broken, or some how flawed. The movie Terminator makes no sense if you think about it: John Connor sends a friend back in time to protect his mother from assassination before his born, but now his friend is his father........ and then you've got Terminator 2 where John Connor is being protected again, so the future still exists.... what the hell!?!?! However, since it's just two movies, with about 4 hours of footage, I'm not too concerned about that. I can endure the temporal loop holes thing and enjoy it. But Star Trek is a series that has far more than 4 hours of footage to it. It has far more than one kind of story going behind it. It's not simply a war against the machines and the constant battle to eliminate John Connor before the war starts. Instead, it's a series that has been on for several years, and spans across generations (pun not intended) of time. There are a few loopholes between TOS and TNG, that always happens when you stop writing tv episodes of that format for over a decade. Despite small lapses, I feel that TOS, TNG, DS9, and VOY have all maintained a least some connection to each other. But Enterprise, after breaking even more 'continuity' things, is just unbearable to me. Almost any plot hole or continuity change can be explained away, as evidenced by some of the replies to this post; but I can only take so many explainations before I just become uncomfortable with it and kind of disregard it. It's like the anime series of Dragonball. You've got Dragonball, then Dragonball Z, which sort of breaks away from the original, but goes on for a really long time, then you've got Dragonball GT. By this point, the story has just become so overdone and convoluted, you just can't watch it. Enterprise has kind of become that for me. I just don't like how it looks. "We're before TOS, we're not nearly as advanced, and yet... it almost seems as if we are...." Just small things like the control panels... I know it's trivial, but I just don't like it. It just looks too modern... TOS is buttons and whirly screws... Enterprise looks like it's ready to take on the Defiant. I know TOS done in the 60's, and that it woudln't make sense for us to have computers in the future that look less advanced than my desktop, but Enterprise just doesn't pull it off that well for me. I just... don't like it. Too bad.
The second half of DS9 was great, but it kind of dropped off in the end. the Dominion War was cool, but I felt it went a little TOO long. It was interesting when the Klingons attacted DS9, but I felt they milked the conflict with the Cardassians and Dominion for just a little longer than they should have. I mean, if the person who played Dax ended up leaving before the show concluded. Not that she's a barometer for a shows quality. I guess one benefit of DS9 being on so long was Captain Sisko. He rocks man! Add him and Worf together, and you have two of the baddest muthas in space.
Voyager had so much potential in my opinion, but it just didnt' go in the direction I wanted. It's not my show though. I felt the enviroment of the crew was just too peaceful. I expected the series to give us a crew that starts as the typical, sterile star fleet crew with high minded ideals and a desire for exploration, but after years of constant hostiliy and conflict with the surrounding galaxy, they become cold, battle hardened, maybe even more ruthless and singleminded in their thinking, the ship never really fully repaired, falling apart in some episodes, the hull becoming less of a standardized star fleet vessel, and more of an orion pirate ship almost.... They did this to a degree with the Borg and a few episodes, but except for that outrageous series finale stuff, not much changed. They didn't seem like a rag tag, on spare parts and glue starship. Everytime foreign parts were added, they just became more powerful, more confident, not more and more uncertain, which I think would have made a more interesting show. I say, stop giving us Star Trek the Next Generation format. Give us Starfleet, but give us a crew that's treading more on the thready side of things, a crew that goes on missions that don't always begin with First Contact and end with happiness. Something where the ending of the series doesn't look peachy keen. But that won't happen. Boo hoo.