Irenicus is a brilliant iconic character, not because of his goals, but for his stellar voice acting and solid dialogues (plus his initial dungeon which provides plenty of background). David Warner elevated the character so much, his lines felt personal and layered.
JonBon is remembered for that because there is nothing more to his character. His voice acting is great and his megalomaniac rants amusing, but he doesn't bring anything more interesting to the table. Not even an engaging conversation, as you can have with e.g. Kerghan.
There was also the "race twist"; I found that to be kind of cool.
