Photorealistic graphics are kind of hard to mask (well). The contrast between the cartoony sprites and photorealistic graphics is easy to ignore if you ask me, and photorealistic graphics can be real... epic, so to speak.
Like in -- unless I'm mistaken -- one TR level that used a set based on a Venice style building. I'm sure I've seen other sets where photorealistic graphics were used well, but can't recall what they were.