It went from good to mediocre, especially after two main cast left (Tony [Michael Weatherly] & Ziva [Cote de Pablo]). The kicker was when Abby (Pauley Perrette), one of the show's main appeals, left. But I think it got bad before that anyways. Prior to all of this, the show had a nice formula of regular crimes & murders, then a special where something spook happens, leading to the death of a terrorist further down. Not anything special but it was entertaining nonetheless. They had some legitimately emotional deaths in their earlier seasons, like Kate, McGee's dad, Gibb's dad, etc. But after all of the major stuff happened, there wasn't really much to continue on and it should've ended.