Halo 4 does look really good, but unless you watch it side by side it's almost like yeah, that's what it looked like but I went back and rewatched some Halo 4 stuff and it's really an amazing difference.
I see so many comments like this with going back to old games.
I don't think I've ever had this experience.
The closest thing I can think of would be rewatching Toy Story recently and being amused at how sketchy the animations were by todays standards, but even that wasn't a huge surprise, and I'm pretty sure that was after over a decade of not watching it.
//==============================
The Halo 4 content is looking interesting. The framerate boost and reduced aliasing certainly has a nice effect...
Would be interesting to hear how exactly they're "improving the shading" in these games. I wonder if it's mostly just higher-precision buffer formats and such... which should do very good things for Halo 4 (probably won't be felt as much in Halo 3 because 2007 Bungie was insane). The weaknesses of the lighting, like poor dynamic lights and objects not always responding well to shadow (i.e. the banshee shot on Exile), are still present.