Maybe I'm biased, since I played Halo: Combat Evolved's campaign likely way over 200 times over the decade, and countless hours in multiplayer, on both platforms. But Halo 2 immediately threw me off balance with the low reticle position, and it has been awkward ever since. This isn't a case of "players need to adapt," it's a case of stupid, unnecessary design decision. I can't think of another shooter that does the same thing, and there's likely a reason for that.