TV is TV, even science shows are more about being entertaining then teaching and informative. You can't expect a TV series to be scientifically accurate, after all if the people producing, acting or writing them where in the field then they would not be producing, acting, writing them they would have an other job to do :)
as for sequels, that is the thing they are often worst (almost always) and they need their own gimmick so they tend to be more exaggerated. If CSI Miami was the same as CSI then why have a second show?