I remember watching this film with my mother when it came out in 2004, so I was 14 or 15. It was a big film because it featured Denzel, but also because of Dakota Fanning.
Dakota was a stand-out up and coming young actress specifically because she could deliver an intelligent and realistic performance as a smart child, but especially because she could do it in serious drama films rather than comedy or family genres.

I remember the film delivering a great experience. American films from back then were usually good more often than not, but this film stood out even among mostly good films. And you are correct about the emotional investment in this film.
As an adult we can sympathize with Creasy and his torment, but we all love the innocence,optimism, and happiness of Pita. And Creasy having to let go of his self-loathing, and being lost. And he finds himself again through the innocence of her before she's stolen from him.

If you like Denzel, have you seen Deja-Vu? I love that film, and that also reminds me of another great movie: Source Code starring Jake Gyllenhall. If you've not seen those I'd highly recommend them both.