I actually like the first game the best (though I've only ever played GoW 1 & 2). The sequel just seemed to nerf so much of the difficulty. I really preferred Rage of the Gods mechanic as opposed to Rage of the Titans in the sequel. I liked how there where a bunch of cheats you could activate to make things ridiculously easy, but I still love and respect the challenge of the very first game.
I also loved the recurring gag of that one Greek citizen who repeatedly gets metaphorically curb stomped by Kratos.