I loved both games, but I preferred God of War II. It still had everything that the first game had, simply more of it, with improved annimations, better enemies/monsters, as well as bigger, more beautiful environments. The boss battles (of which there were more) were legendary, and the brutality of the combat had been raised. And I found the story in II to be the more interesting, more appealing tale.
I've never agreed with the reviews that put God of War II just below the original title, because for me it's a tad better in every available aspect, and as thus should be put a shade ahead of the original. IGN and Gamespot both rated the sequel with a 0.1 reduction on the score of the original. When in fact it should have been, in my opinion, at least a 0.2 in the opposite direction. But I think they made that impossible by rating the original a little too highly, at least in regards to IGN who scored it at 9.8, when a 9.3 (which is what Gamespot scored it) is more accurate.
But at the end of the day they're both great games. Two of the best released for the PS2. And God of War III is my most anticipated release for the PS3 as a result.