Just thought I should look up the original Wolf3D and Spear again, realizing I haven't played those games for a decade. Then I discovered I don't have them on my machine! Very well, I shall have to dig out that machine in the basement again.
I think I played the original 60 episodes at least twice, some of the episodes I played three or four times, Spear only once. Not that much really when I come to think of it, but I have very vivid and visual memories of many of the levels.
All episodes had something special to remember them by. I have fond memories of episode 1, being the first and quite a novelty, especially level 7 made an impression. Episode 6 is my favourite overall, episode 2 was the most atmospheric, episode 4 had some really challenging levels, episode 5 was fast paced and episode 3 made you fight Hitler! This of course is a general description, when you get down to the individual levels most of them had all these qualities in some respect, especially the later levels and secret level of episode 6 had it all. Spear had all this too and was generally more difficult. The Ubermutant level being my favourite.
For me it was the combination of the fighting, the exploring, the atmosphere, the story and the personalities of the boss enemies that really made these games stand out!
Many later comparable games lack much of this. Despite many new features the main attraction seem to be just roaming around gunning down hordes of something. You soon get the feeling "Oh no! Just more of the same." And the boss enemies aren't really interesting. Compared to Wolf3D and Spear many games just lack personality.