You people dissapoint me...
Pixel art is about expression yourself in a medium where the size of the smallest grain matters, no more, no less.
I create my pixel art with 3D programs, generators, filters, photoshop, the whole smack. I always make sure the options allow me to keep full control, and that's it.
Pixel art is not the tool you use
Pixel art is not the ammount of time you put into it
Pixel art is not an art style
Pixel art is not defined by colour count or size
Pixel art is not the individual placement of pixels
-> Pixel art is about working with the disabilities that come with the size of a pixel
Individual pixels are visible, so a single pixel can mess up the look of something, creating the need for an almost pixel perfect execution. Since the size of a pixel is technology based, pixel hand goes hand in hand with other restrictions such as colour restrictions, size restrictions and other things, but they are just intimately connected to pixel art. Isometric magazine art drops all the other restrictions and just uses the visibility of the smallest part as a stylistic bonus for example. That's why you won't find too much AA in those pieces. Once a pixel becomes invisible due to the medium, as is the case with higher resolutions or CG art, where the pixel becomes invisible because it's surrounded by too many others, it loses the right to call itself pixel art. A correct definition for pixel art would be:
The art of working with or around the visible size of a pixel