Halo Combat Evolved is a groundbreaking but flawed classic. When it hits it hits but then you have missions like the Library that are just a slog and a lot of reused levels. Not really much interesting to say. Fantastic game that had sequels and prequels that were simply better. Well some of them.

As for the Anniversary changes themselves, yeah it suffers from "let's make everything brighter!" and as a result sacrificing part of the tone and atmosphere. Letting you switch back to the old graphics while maintaining the upgrade in performance is still worth it though and I'd be lying if I said there weren't some changes I like better.