Between those four choices Quark is the best option.
Rom is the most well-intentioned of the group, but a leader needs good intentions and common sense. I imagine a year after Rom became Nagus, the grand treasury ran out of money and they started borrowing money from Romulus.
Quark is greedy but he's also got just enough empathy to make life bearable for the poor and to avoid doing business with mass murders, and he's got enough fear to want to make the people happy with him.