I would go with GoW III, but there's a big caveat to it. Have you played any of the previous games in the series before? GoW III kind of requires that you have played 1 and 2, and in a way the PSP games (Chains of Olympus and Ghost of Sparta) to really get the most out of the story. Without the backstory, however, it's still a fantastic game. It is generally harshly criticized not because of the game itself, but because GoW 2 was such an amazing game in all aspects that it set the bar for 3 waaaaaaaaaaaaaaaaaaaaaaaaaaaaay too high. (Unreasonably high as far as I'm concerned).
If you haven't played the previous titles in the series, then I would suggest taking your money and getting the HD Collection and, if you can afford it, the Origins Collection so as to get the backstory to the game. (Or go to YouTube and watch a playthough of them in order to get the storyline).
I personally found GoW 3 to have some incredibly awesome parts, and some frustratingly difficult and slow parts as well. Visually, it's quite beautiful and the sound is incredible as well just as it has been in the full series. I'm as far from a "It has to be super impossibly difficult and only played on the highest difficulty possible to enjoy it" type of gamer. I like enjoying the games and playing it on a "normal" or "easy" level so that I can enjoy the game and story and not get frustrated by the difficulty in it.
A few areas in the game that really stood out to me were the battle with Hades, the Garden section with Hera, Aphrodite's chamber, and the encounter with Cronos.