If they came out with a new DOOM 4, The best improvment would be the secrets to find. I was quite disappointed in Doom 3 and their lame attempt at this with the lockers and codes, very boring. Half the fun of playing the DOOM games was finding all the secrets in each area.
I liked the lockers and codes and such but agree they need to bring back the old style of secrets. They certainly could have both and make it more fun to explore and find stuff that is hidden better than some armor shards under a dark set of steps.
