I think Halo 2 separates from Reach in the encounter design. Aside from sniper alley, Bungie put you in some dope scenarios.
I would ask JC to get in on this discussion but that nigga thinks Silent Cartographer and the Two Betrayals are better levels than Assault on the Control Room, so he can't be trusted.
It's funny, despite the linearity Halo 2 really managed to nail the sense of
scale, though. Some of the tricks were more obvious in hindsight (like the "pseudo-skybox" they send you through after lowering the shields on Sacred Icon), but
man, they really did a good job at establishing you were a small fish in a big pond exploring Delta Halo, Sacred Icon, High Charity, etc. All the vistas felt like they were strung together a lot better than those in say, 4, where you just kinda teleport where you're needed.
One thing I also noticed playing through H2A was how great they handled things going full-circle with Chief and Arbiter's stories: Chief ends up tearing his way through a politically awry High Charity, and Arbiter finally sets foot on a practically pristine Halo.