Towards the end of SG1, I didn't think the story lines were all that great either. But I still found a lot of enjoyment in the characters. They were characters I knew, and there were always humourous interactions and inside stuff between them. That was what kept me interested until the end.
Atlantis didn't grab me as much. The characters were okay while the story lines were just more of the same from SG1. I watched it through to the end, but it wasn't as good IMO as SG1.
Now SGU however, I didn't like at all at first. I toughed it out through the first 10 episodes, and then just kind of gave it up. I liked the idea of more varied and flawed characters. Definitely a departure from the clear good/bad divisions in SG1 and Atlantis. But I don't enjoy the only unifiying plot being "we need to find a way home..." It's been done before so many times, and ends up being something you know they are never going to achieve, at least not until the series ends.
But one day I was hankering for some Sci-Fi, and preferably Sci-Fi I hadn't seen, so I gave SGU another shot. I thought the last 10 episodes of season 1 were an improvement. Enough that I went ahead and watched the first ten of season two. Season two was even better. The subplot of figuring out what Odyssey's true mission is, was much more interesting to me.
I'm not surprised that it's going away, and of course there's no way of knowing if they would have kept improving, but I am looking forward to the final 10. I hope they do wrap up the true mission story, and finally get home. But yeah, I don't expect it to go anywhere after the last 10 are over. I do want more Stargate from MGM, but I'm not holding my breath.