The way I use them, "pixelated" refers to images rendered to a target resolution in pixels. "Pixelized" refers to an image that is transformed to resemble pixel

The way I use them, "pixelated" refers to images rendered to a target resolution in pixels. "Pixelized" refers to an image that is transformed to resemble pixel art of lower quality (in terms of resolution and color depth). A screen from Super Mario Bros is pixelated. That's what the art is supposed to look like. A screen from Broken Age running in Retro Mode is pixelized. The art isn't actually intended to look like that, and it's just for nostalgic effect.