1. Plastic look / Uncanny Valley.
That's mostly consequence of (ab)use of specular combined with low-res bumpmaps. Pretty widespread, alas.
2. Favoring realism over art style
I've never had any problem with it, at least not since doom engine games and pixel art - back in those times there were many gorgeous stylized sprites and backgrounds.
If anything I have problems with stylistics based on abuse of cinematic effects - DoF, bloom, lensflares.
I do have problem with lack of good art direction, though, and stylization, like in DX:HR can work sometimes.
3. Questionable effects like ambient occlusion, bloom/HDR, motion blur, depth of field etc
I don't see anything wrong with AO. It's merely poor-man's self shadowing that can be applicable to ambient lighting.
Bloom is shit unless used only for extreme lighting, HDR can be shit if abused, DoF is almost invariably shit (Skyrim seems to be p. monocled in this regard as it only applies DoF in menus, underwater and during cinefaggic takedowns, no excessive bloom either - it is pretty plastic, though, although it looks much better if I apply my monitor's postprocessing in the form of saturation and sharpening filter to it).
Concerning graphics, what makes a game look great is having the the textures at the highest possible resolution.
This. No need to use texture packs, TBH, for example Morrowind's textures are already comparatively hi-res.
Apart from lighting it also used some texturing tricks - for example recursively applying scaled down detail textures to surfaces to introduce feeling of detail and avoid smeary look.
Nope, sorry. Looked like shit since day 1.