Literally every skybox in the series has some "matte painting"-ness to it. Those celestial objects in the background in Halo 1 sure as hell aren't spheres of polygons.

Kind of surprised it isn't more obvious. There are relatively few games on PS360 which successfully conceal the fact that their backgrounds are heavily comprised of textured-in objects, and most of them accomplish it by shoving the game through a blender full of vaseline. FFXIII is the only exception to the vaseline that I can think of off the top of my head, and it's using what looks like a very clever combo of 2xMSAA (on geometry) and slight negative LOD bias (on textures) to produce shocking consistancy between textured details and geometric ones (and even then, the game hardly succeeds at this consistantly; the Hanging Edge absolutely nails it, Eden not so much).