Riquelme, is the most similar, to Veron. I would say that Montenegro of Independiente and Gonzalez who plays for Rosario Central also have a resemblance to Veron.
Their is another player who has come up from the youth ranks at River Plate. His name is Andres D'Alessandro, he is only 19 years old and has played for Argentina's youth teams U-17 and U-20. He has already made his senior debut for River Plate. He will slowly start to get more playing time on River Plate's first team. Back in February, Liverpool and Chelsea of England were very interested in signing him. Anyway, you'll be hearing more about this player in the future, his footballing style is very similar to that of Veron's.
Aimar and Romagnoli, are very talented but have different style of football.