What I like about Command & Conquer and Tiberian Sun with regards to world building, story and lore:
*The alien substance Tiberium that at an increasing pace transforms the Earth into something unrecognizable
*Tiberium is a great resource but at the same time very dangerous. Should humans embrace it or eradicate it? Is there a middle ground?
*The mysterious character Kane who seems to have lived on Earth, stranded, for a very long time, biding his time in anticipation of the arrival of Tiberium (Kane is apparently inspired by
this Asimov short story)
*The biblical stuff
*The dynamic where Kane wants humans to accept tiberium and let it bring the next step in the human evolution whilst GDI wants to control tiberium and possibly get rid of it
*Cool units
*The artstyle
*Tiberian Sun introduces "the Tacitus" a device of Alien origin that keeps knowledge of Tiberium. Useful if it can be decoded
*Kane has used the Tacitus to build alien stuff
*Who are even these aliens?
*Who is the mutant leader Tratos and why was he able to translate the Tacitus for Kane?
There's a lot of mystery to the whole setup but unfortunately EA kind of ruined it with Tiberium Wars that's just basically
War of the Worlds without the interesting stuff from the two former games. However it's unknown if Westwood themselves could have pulled off that great story-based sequel? I don't think they treated the story and lore with respect with what they did with C&C Renegade which could have been a great opportunity to flesh out the story and lore of the first C&C.