Silver Dollar City http://www.silverdollarcity.com/ in Branson, MO rates between 3 and 4 stars for me. I've been 3 times there, and overall I find it an okay theme park. It's unique, since the people who work there wear old-timey clothes, and there are shops that actually make candy or soap or whatever else right in front of you and you can sample it or buy it afterward.
There are some fun rides there. I don't think they quite compare to Six Flags, but they are pretty good. The last time I was there (Nov '06) I enjoyed the new upside-down roller coaster called Wild Fire!!! I rode it twice in a row. Oh, the park closes at 9 (at least it did the night we were there) anyway, all the older people who are there only for the shows left at 8 so we had an hour to nearly ourselves to do whatever we wanted.
This is definitely a theme park I recommend if you're in Branson, even if it's not 5 stars to me.