Depends what reviews and previews you're reading. Most of the ones I read focus on the whole package.
Sure, modern next-gen games such as Mass Effect, the Orange Box, Gears of War, Halo 3, Call of Duty 4 and Crysis have amazing (and at times realistic) graphics, intuitive controls, wonderful sound and intelligent AI. These features form a cohesive package which is fun because it is immersive; you, the player, find yourself more connected to the game because of it.
Hell, I can play Rocketman on facebook for 20 minutes and have 'fun', but it's not a particularily immersive experience.
I think that graphics, AI, etc, get alot of mention in the press precisely because they do factor in to the 'fun factor' of a game. 'Gameplay' itself is most important, of course, but that's a very vague term. What we 'play' in the 'game' is what we actively experience in it, and I'd argue that we experience real immersion with the help of great graphics, sound, AI, and so on. The aesthetics of a game - how we perceive the game - is our most significant connection to the game itself.
The latter features aren't just found in next-gen games though: throw on Mario 64 and the graphics, controls and sound are work together to provide a more immersive experience, and therefore help make the game fun.
If you're making the point that games reviewers/previewers don't focus enough on critiquing games, I'd have to agree. Far too many articles I read are simply descriptive, explanatory pieces: e.g. "You can get Mario to do spin attacks by shaking the wii-remote" instead of "Shaking the wii remote to spin Mario is an [ingenuis/strange] decision because [insert critique here]".