Halo is one of my favorite games of all time, but a few of the levels were an absolute drag. Assault on the Control Room was waaaay too long, and to make matters worse, Two Betrayals was the same long-ass level, but backwards.
If I were to completely redo a level from scratch, that would be the one.
I tried Halo for the first time last year. I had not tried any of the Halo games before. When the original came out I was broke and in the military so I didn't have a chance to play it.
I don't know if it's just me, but the original Halo is boring. I spent an hour or two running around different environments shooting the same two or three enemies, or in one instance hiding in a hallway and popping out for a couple of shots so some hilariously suicidal officer I was escorting didn't throw himself on the nearest armed alien and die. The whole thing just drags.