I was looking at the CIV 6 achievements stats, and realized I could approximate who the most/least popular Civs were by their winning achievement percentages (I'm aware this is not a perfect science, so to speak, especially with such small differences in percentages).
For the curious:
8.4% Win a regular game as Trajan
5.4% Win a regular game as Frederick Barbarossa
5.2% Win a regular game as Qin Shi Huang
5.1% Win a regular game as Theodore Roosevelt
4.5% Win a regular game as Hojo Tokimune
4.3% Win a regular game as Peter the Great
3.8% Win a regular game as Catherine De Medici
3.5% Win a regular game as Tomyris
3.5% Win a regular game as Cleopatra
3.3% Win a regular game as Victoria
3.2% Win a regular game as Gilgamesh
3.0% Win a regular game as Mvemba a Nzinga
2.8% Win a regular game as Gorgo
2.7% Win a regular game as Saladin
2.6% Win a regular game as Pericles
2.3% Win a regular game as Montezuma
2.2% Win a regular game as Gandhi
2.1% Win a regular game as Harald Hardrada
2.0% Win a regular game as Pedro II
1.7% Win a regular game as Phillip II
Rome by a mile basically (and poor Phillip clearly the most disliked). Some things are a surprise though - the Greek leaders are lower than I'd expect (maybe because there are two?) and De Medici is higher than I'd expect.
For the curious:
8.4% Win a regular game as Trajan
5.4% Win a regular game as Frederick Barbarossa
5.2% Win a regular game as Qin Shi Huang
5.1% Win a regular game as Theodore Roosevelt
4.5% Win a regular game as Hojo Tokimune
4.3% Win a regular game as Peter the Great
3.8% Win a regular game as Catherine De Medici
3.5% Win a regular game as Tomyris
3.5% Win a regular game as Cleopatra
3.3% Win a regular game as Victoria
3.2% Win a regular game as Gilgamesh
3.0% Win a regular game as Mvemba a Nzinga
2.8% Win a regular game as Gorgo
2.7% Win a regular game as Saladin
2.6% Win a regular game as Pericles
2.3% Win a regular game as Montezuma
2.2% Win a regular game as Gandhi
2.1% Win a regular game as Harald Hardrada
2.0% Win a regular game as Pedro II
1.7% Win a regular game as Phillip II
Rome by a mile basically (and poor Phillip clearly the most disliked). Some things are a surprise though - the Greek leaders are lower than I'd expect (maybe because there are two?) and De Medici is higher than I'd expect.