I'm pretty surprised that people hate reach's campaign now. I have recently played through the entire series again (sans Halo Wars), and I still say Reach is the best, with 3 being the only one to surpass it in certain areas of gameplay, such as vehicles.
I really don't understand some of the complaints. The sandbox is bad? In my play through, I used more or less every weapon. The story sucked? Eh, I guess, but so did all the other Halo's. I felt that reach actually did a pretty good job by Halo standards. Uninteresting level design? What? In terms of gameplay, it allows for open gameplay like no other. In terms of visuals, you'll have to expand on that one a bit, because I don't see what you mean at all. There were skyboxes, covenenant cruisers and strongholds, shit being destroyed, etc.
I especially don't really understand why so many people hold CE on such a pedestal. Don't get me wrong, it's a great game, but it's been surpassed in so many areas that when I went back to play it, it felt outdated to me.