Doom 1 & 2 also had a novelty factor at their time. FPS games were few then, and they were kind of the best. I also enjoyed Duke Nukem 3D, well I liked it lamost better than the Doom games, as well as Descent II. All thjose games were “cool” becuase unseen before, and very exciting for this.
Now, 20 years later and with countless games in the genre, it’s just not the same anymore (and playing the old games again isn’t the same either, becuase we are now 20 years older and have experienced 20 years of game eveolution …)
I must admit I haven’t even taken a real look at Doom 3, because I thought it’s “just another FPS”. And I do not expect anything in particular from the source code that would help me to make games.