For me:

1. God of War 2
2. God of War 3 (epic boss fights helped it, cause the gameplay part going through Olympus all the time and the art style were worse than 2 & Ascension)
3. God of War Ascension
4. God of War

Didn't play the PSP ones, maybe on the Vita.
Funnily enough the order I played them in is GoW3>GoW2>GoW:A>GoW(started it before Ascension but didn't finish).
That's the reason I don't care about the supposedly progressively worse story in each game, cause well Iplayed the franchise backwards
They all have an amazing gameplay though, maybe my favourite gameplay in a game ever. That's why I hope we'll see another GoW game on the PS4 asap. And the fact that Cory Barlog (GoW2) is back on board again, makes me very excited!

It's not that it was a bad game it just lacked what the previous iterations had, well paced and epic feeling. The beginning was epic and the ending was epic, but everything else was just forgettable.

GOW2 > GOW3 > GOW > GOW:GoS > GOW: A > GOW:CoO

GoW1>GoW2>GoW3>GoWA

I know this looks like a hipster list but I'm ranking the games by variety and for me pretty much nothing can beat the fight against Ares.

I got into GOW actually by accident when I was looking for PS2 games to play on my PS3(because I never owned a PS2). I saw GoW2 in the bargain bin and I remembered having read some people recommending this. At the time I didn't know it was part two thanks to the awful cover art. It was quite fun and then right after that I got me part 1 which was even better.
Then GoW 3 came along and it looked as if the developers had thrown all the interesting puzzles and places under the train just for more spectacle. The game was a lot shorter and the puzzles were a joke, still had a somewhat engaging story.
GoW Ascension was by no means a bad game but it just felt like a cookie cutter GoW game. It was fun and new but just couldn't excite me like the other 3 did. I probably would've enjoyed it more if it were my first.

1.Ghost of Sparta - really unbelievable for a handheld and great gameplay with a spectacular ending
2. GOW 3 - Nothing defies epicness more than this one
3. GOW 2 - Really great (my first GOW)
4. Ascension - It nearly reaches GOW 3 levels of epicness but that took to long to reach.
5. GOW 1 - Thought it was a good game but after playing every single one of them this wasn't as epic.
6. Chains of Olympus - Good

Really if I would give marks on this than everything will be between 8 and 10

Played all of these on PS3.

GOW 2 > GOW: Ghost of Sparta > GOW 3 > GOW 1 > GOW: Chains of Olympus

Haven't played Ascension yet.

God of War 3
God of War 2
God of War 1
God of War Ascension
God of War Ghost of Sparta
God of War Chains of Olympus

Sorry for that, that sounded better in my head than while writing(Im not an english native speaker) but in general I didnt like the puzzles, the combat or the story

i only played 3 of them and i rank them base from the whole game excitement experience they gave me...

God of War 3 > God of War Ghost of Sparta  > God of War Chains of Olympus

will hype for new God of War series on PS4...