Originally posted by Tzeentch
Ulic gets no play because hes's basically just a less whiny Anakin. At this point in the mythos, the only thing more cliche more than a megalomaniac is a Jedi prodigy falling to the dark side, becoming a megalomaniac and then feeling bad for doing megalomaniacal things and dying.
Ulic's story is more complex than that. He was actively trying to work as a spy for the Jedi against the darkside. And he actually lived years and years after returning to the light.
Exar was a Jedi prodigy who fell to the dark side out of direct desire for power... that's even more Anakin than Ulic is!
Exar Kun is a much more entertaining sith in all his greasiness, and with decent writing could be the Star Wars equivalent of Morgoth.
Really, if you need to add a 'with decent writing' provision, that could apply to almost anyone. Why Exar and not any of a wide number of others, is what I'm saying?
Also, Sith-history wise, Exar wasn't... that crucial. I mean, he was one of the early 'master and apprentice' pairs that the wider galaxy knew about, but he didn't found an order. He didn't take down the Jedi. He was famous but didn't represent a turning point.
Heck, he's kinda redundant with Bane....