I have to say I think the acting and characters on TNG was a lot of what made the show work for me. Especially if you watch the first season and realize how completly stupid some of Stewart's lines were that he pulled off, I really think the cast is what made that show work so well. There wasn't a character I didn't like (except for Yar and Polaski, who fortunately didn't last long enough to count).

I don't dislike Sisco, but he didn't do much for me either. I gradually just got too busy to watch DS9, so if some of the characters improved I didn't notice. I completly agree about Seven, she was one of best Star Trek characters ever.