I think that the "formal" rules for pixel art have become more well defined with increased access to the internet, and you now see more of a tendency towards Japanese / console style pixel art (compare with Deluxe Paint-style pixel art seen in old PC games). I think that there is also a huge amount of "abuse" in these rules, some of which are definitely universally applicable as applied to pixel art, IMO - namely, using the same pixel size, and perhaps keeping the palette reduced as far as reasonable. There is quite a large amount of "bad" pixel art, probably more so than "good" pixel art, so it is easy to come to dislike the genre nowdays. But pixel art (at least "good" pixel art) is much harder to produce than vector art or unrestricted raster art, especially when it comes to animation (unless you are just rotating limbs, which is a "no-no" in pixel art rules).