It's more to do with the fact that NCIS is just so entertaining and that's mostly (if not almost entirely) because of the people and performances who characterize it. That said, I was quite impressed with this first episode.
Chris O'Donnell and LL Cool J do not add up to Mark Harmon, but they can lead a show. They complement each other on levels of physical presence, facial expression hilarity, and general attitude. There are obviously some flubs that will hopefully get ironed out over time. For one, LL Cool J is not a great stage fighter. That can be fixed. What may not be fixable is the fact that it took me most of the episode to realize that "G" is actually O'Donnell's character's first name. Or initial. Apparently he doesn't have a first name. (Cue eyeroll.) Maybe that's just an overly melodramatic choice by the writers. Or maybe they're trying to help LL Cool J acclimate by letting him add "G" after every other sentence. Your choice.
As for the rest of the NCIS: LA team, I was not impressed at the beginning of the episode, but they managed to grow on me by the end of the forty-some minutes. I don't think any of them are going to be nearly as out there or as independently hilarious as the original NCIS team, necessarily, but maybe that's a good thing. Nate the psychologist (Peter Cambor) and Dom the newbie (Adam Jamal Craig) are my favorites so far. I'm on the fence about Hetty (Linda Hunt), who is basically Edna of The Incredibles come to life (and also actually the voice of Pocahontas' Grandmother Willow). But I'm not hating anyone on the team, not even the token female character, so things are shaping up.
The trick for NCIS: LA is largely to distinguish itself from NCIS, because a direct comparison is just going to work against it. Unlike the three CSIs, all of which can be broken down into more or less the same exact structure, the world of NCIS is less about the evidence and more about the characters. Or it has been. But the case for the NCIS: LA team in this first episode was phenomenal - far more intriguing and detailed than most NCIS cases tend to be. Maintaining that dedication to storyline is, I think, the best hope NCIS: LA has for survival...that and the fact that it airs right after its progenitor on a night that, so far, has no real competition from other networks (not in my world, anyway).
I'm going to need to see a few more episodes of this show before my opinion solidifies, but the prospect is looking pretty good so far.
(This review also posted on my blog at http://meltedbrain.wordpress.com)