For me, the appeal resides in certain characters - those with a definite IN** preference and a slight T leaning. Sounds familiar doesn't it... While there's some real science in CSI and Numb3rs, it's really there just for the effect more than anything else. The wow-factor high-tech professional aura.
In CSI, the character I identify the most with is Sara Sidle. Too bad she's not part of the regular cast anymore... And yes, she's a huge science nerd. I also somewhat identify with Gil Grissom because he and Sara are of a similar type. Although I have mixed feeling about the romance between them because I've always thought of their relationship as mentor/protégé or father/daughter... And though they could seem cold and unapproachable, they're really big softies inside :-P
Needless to say my favorite character in Numb3rs is Charlie Eppes. I'm not as quick-minded as he is, and nowhere near being able to scribble mumbo-jumbo equations at a rate of 1.5 lines per second. Although he reminds me of a certain someone when he encounters a Eureka moment, hmm. Charlie's girlfriend/later fiancée is a professor as well... not surprising.
((Aside)) I can empathize with Lisa Simpson sometimes... though she seems to be an ENFJ. I guess it's her musicality and precociousness. From the circumstantial evidence I've gathered, I was a precocious and misunderstood child who "could have turned out less psychologically damaged". ROFL.