The Reason Zenos.

[MoofiaBossVal]

When comes to XIV villains, Zenos is far and away the most iconic.

Let's go through the list of villains:

Bahamut: he was a non-character, effectively a force of nature. he only has relevance to 1.0 players and those who did the Coils, which is content the vast majority of players have never touched.
Gaius van Baelsar: Appears in a grand total of 3 cutscenes in 2.0, and isn't even the final boss.
Ultima Weapon: A non-character.
Lahabrea: is a pretty forgettable generic evil guy. Only becomes somewhat interesting in retrospect once ShB dropped.
Thordan: is a generic evil JRPG pope.
Nidhogg: is a generic evil dragon. He has so little characterization that he borders on being a non-character.
Fordola: is a lieutenant to the big bad and is more heroic than evil.
Yotsuyu: spiteful, psychotic woman who gets a sob story later on. At least she has a cool character design.
Varis Zos Galvus: Doesn't do anything of note.
Ranjit: Forgettable.
Vauthry: Served his purpose but isn't memorable.

The only memorable, good villains are Zenos and Emet. Zenos is the most classically villainous, has the most iconic character design, and has combat capabilities most adaptable for a fighter moveset. He has the most appearances of any villain, appearing across three expansions (probably four), and is treated as the WoL's arch-rival.

The jury is still out on Elidibus. He has the potential to be just as memorable as Zenos and Emet. It looks like they're setting him up to be the ultimate jerk of the XIV setting and the WoL's timeless arch-enemy. We'll see.