Michael Oeming wrote the first Ares mini-series, and while the character had yet to get the pretty cool visual look he would adopt with the Avengers, the story was absolutely phenomenal. There are times when a creator reinvents a lesser known character without needing a cross-company crossover or deals with the devil, and this is a perfect example done exceedingly well. I don't want to spoil it if you hadn't read it, just do yourself a favour and check it out.
The second mini-series was written by Kieron Gillen, who has a true knack for writing mythological characters. Again I don't want to spoil anything if you hadn't read it, but it really explores the God of War's true character. The best part about both of these mini-series' is they are collected in the same trade paperback, and I believe that it is the same price or cheaper than buying the first one buy itself! So now you have no excuse to check them out!
Unsurprisingly, Ares also played a role in The Incredible Hercules, particularly in the first story arc or two. The story takes place during the Civil War, where Ares is a fully deputized agent of the law, while his brother Hercules is a wanted fugitive. Holy role reversal Batman! In one of the funniest fight scenes I've ever seen, the still-pretty-morally-ambiguous Ares cannot resist using his newfound authority to kill his hated brother.
Ares met his end in the Siege mini-series, but he really showcased a sense of honor that I'm a sucker for in these warrior type character, and it was then that I could really, truly accept him as a hero and not a villain. He certainly started out as a villain, but he quickly revealed that he is far from being a black-and-white character.