Throughout the series, there have been many genjutsu users who proved their merit and likability at one point or another. However, some of them are cooler than others with their unique qualities and appealing designs. Moreover, one gains a better grasp of their usage of genjutsu, as no two practitioners are completely alike.
As a sharingan user, Kakashi is familiar with genjutsu. One of the first characters to debut, he posed a moral question to Team Seven that defined their ninja careers about putting comrades before the mission. It was a lesson that he learned personally from his father and remains a point of contention well into the sequel series.
Kakashi is the coolest genjutsu user due to his relaxed attitude, experience as an Anbu operative, and willingness to take down targets he feels cannot be redeemed. His balance of compassion and grittiness makes him a well-balanced, enjoyable ninja to watch.