Except Halo 4's linearity had nothing to do with technical limitations.
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Linearity is fine, as long as it's fun at the same time. Halo 2 while rather linear in its level design, was a hell of a lot of fun. As was Halo 3. So it really didn't matter so much - at least to me. Halo 4 however, not only has tedious gameplay with dull and repetitive enemies, but the levels are equally as boring and only serve to shovel you down into the same tedious and uneventful set pieces in which you have no control over. That Mammoth mission is the worst thing I've ever experience in a game. Disgusting.
I think that is one of the better missions in Halo 4? You don't need to stay on the mammoth at all, and the big vehicle canyons provide you the chance to take down the enemies in numerous ways and different paths.