Not sure exactly what it is but I jes' luvs me some CSI:NY. I like the vanilla Vegas CSI too but I like this one even better. It could be that NY does great engaging character interaction even better than the original does.
It's also still got a bit more... something significant about it. I really liked how in the first season the mood was downright Gothic (makes sense, being set in Gotham, and all). It happened in the basement, everything was washed out and blue, the crimes were more brutal than ever. Of the three shows this one established itself as the horror-tinted procedural crime drama. Apparently it didn't sell well enough, so several noticeable measures were taken to "lighten up" the show. Brighter colors, more humor, a new penthouse crime-lab for the crew... meh.
But still, the one thing they couldn't "spruce up" were the gritty and dynamic characters. I think I fall for these folks so well because they clearly care so much about each other. In that bleak and morbid world they inhabit the only thing that keeps them living is their undying loyalty to their friends and their unflinching dedication to doing their noble work.
I'm a character guy. Plot's fine and dandy but honestly I can do without it if the characters of a story are complex and engrossing. And this show just plain has the best characters and relationships of aLmost any I've seen. Take Danny Messer and Don Flack for example. These guys are card-board-cutout New Yawk tough cliches transformed into living breathing people like old Geppetto must be their dad.
Anyway... it's good. Check it out!