NCIS is, in reality, unlike any other show. I suppose you could say it falls into the procedural drama genre, but on some level it doesn't. It follows the Naval Criminal Investigation Sevice as they solve cases involving the navy and naval officers. NCIS manages to combine the seriousness of the crimes faced with the immense chemistry that shines within the cast. Bring that together with the great humour and stella writing, and you have a great show.
I suppose one of the things many people seem to dislike about the show is that no one is safe, and despite being able to get the viewers attached to the characters, the fact that any of them could go at any time is always over us. However, I feel thats a fact I like about the show. Surely, its a lot more respective of life. Working as an NCIS agent would be dangerous, and people would leave and new people would be hired. That doesn't change the fact though that it pains me to think of any of them leaving... but its something I have come to trust the writers over. Losing Kate, I thought was the end of NCIS, but it went from strength to strength showing the calibre of the production team.
Perhaps, for me, the best thing about NCIS is the interactions between the characters. Tony in particular manages to make me giggle as he bickers with Ziva, patronises McGee and tries to appease Gibbs. That is something most procedurals lack... the humour between characters, and NCIS does it so well.
Overall, although the fate of the characters in NCIS may be uncertain, it certainly is a show I hope will be around in years to come... if only to see Tony and Ziva get together!