I've often wondered about this one myself.
Personally, if Menem had won things would have gotten really "interesting", but Duhalde had three candidates before Kirchner: the orthodox Peronists Felipe Sola of Buenos Aires and De la Sota from Cordoba, and this man:
General politics:
-Carlos Reutemann, as a moderate right-winger, would not have entered into an alliance with Venezuela, but we would enjoy cordial relations with the USA, Europe, Colombia, Chile and Brazil.
-His record as Governor suggest that he would have used the Economic Emergency Laws the same way as Kirchner, and centralized power way too much. He's a Peronist Caudillo after all.
-He continues with Lavagna's and Duhalde's policies, before turning Fiscal Conservative. By attracting investors and not having crazy projects like the Caracas-Buenos Aires oil pipe or the Tren Bala, he might get actual money and will not alienate the Paris Club or the FMI.
-He doesn't attack the Church and the army.
-He wins a solid majority and unifies the party by 2005-2007.
-He is reelected in 2007.
-I don't know whom his vice president might be, probably one of Duhalde's men. Let's say Felipe Sola.
-There's still corruption scandals, but no suitcases from Venezuela, no Tren Bala, no Luis D'elia, no lockdown nor war with the agro-industrial complex, no nationalizations or nationalizations to a minimum. No attempts to take all that money from the agro producers of the retirement pensions.
-Doesn't vindicate the left wing terrorist groups, but might still have Cafiero and the other one in his cabinet.
-The CGT might no split? not sure.
Opposition:
-A strong united PJ in 2007 forces the opposition to a different direction.
-Julio Cobos never rises to prominence. Same for Alfredo deAngeli
-Macri's options are more limited. Perhaps an alliance with Carrio? a coalition between the UCR and the CC might happen earlier, perhaps with Macri as the third wheel?
Other:
The economy is overall better since the President doesn't support Chavez, attack the USA and the business classes nor is crazy...nor does he hate capitalism.
A Third term in 2011? Hard to say, Lula and Uribe don't seem to be going for it...and he's not the Chavez type...either his VP Felipe Sola or opposition leader Carrio replace him in 2011.