The piecewise gamma curves on Xenos' I/O sometimes do result in some crush, but the difference is usually not even close to that extreme. And even some multiplats correct for it well enough that the discrepancy between PS3 and 360 is nigh-on nonexistent; Halo 3 was built specifically on that hardware and intentionally designed with a relatively vivid style. If Bungie had wanted it to look like the XB1 version, it would have defaulted to a little higher brightness at the least.

I've got my TV set up with relatively mellow settings, so most things look fairly natural on it, but I always feel like dark regions in Halo 3 MCC look washed out. You can often make out some details better, but it doesn't feel like it's how it's supposed to look.

Weirdly, the MCC version also suffers from more obvious banding than the 360 version; it's not noticeable in most areas, but the sky on Floodgate is particularly absurd.
(I'm left wondering if this is due to a buffer format change, the weird luminance curves, or both.)