NCIS = good show. Particularly after Ziva joined and Kate was killed off.
NCIS LA = meh. character depth and realism is less. Sort of like CSI Miami. Few things in it are likely and it's just there to be flashy and have nice special effects and scenary. (I can't stand the entire CSI series. Completely lacks any realism. Oh yes we lifted your fingerprint off of extremely rough and pourous concrete. Unlikely. Not to mention you don't dust an entire driveway for prints. Law & Order SVU also to some extent suffers from this, with over sensationalized things. Even the original Law & Order to some extent. But L&O the original is the most like real life out of the CSI series and L&O series. Although L&O often gets things wrong as well, and well... I like the cast of L&O better than SVU also.... except for Munch!.... Det. Munch... played the same character on 4 different networks (FOX, UPN, NBC, HBO) and 8 different series... Homicide, L&O, L&O SVU, L&O Trial by jury, The Beat, The Wire, X-Files, Arrested Development. (Homicide for its time was the best and most realistic cop show around... at least in the early years... towards the end they were grasping for love stories and crap to try to get more viewers and ended up ruining the series).
Anyway old NCIS episodes might not be available legally online, but more recent ones where. I think cbs's website has the most recent episodes on it, as well as several months ago I think there was an AOL website that had them on it as well. NCIS is a show though that is best if you don't just watch it once and awhile, you'll get the most out of it if you watch it continously and learn the storylines and character development.