Eh, since all the big ones have already been mentioned (though I will still continue to stress how much The Last of Us belongs to every PS owner's library), I'll just tell you to get the GoW Collection 2 and God of War III. Chains of Olympus and Ghost of Sparta aren't phenomenal by the series' standards, but are nice chunks of the good God of War gameplay, and Ghost of Sparta fills some gaps in the story that were hinted at in III.
God of War III is IMO the best in the series. The gameplay is absolutely phenomenal, as well as the pacing, bosses and the visuals. Some sights will still blow you away 5 years after release. The story seems to be quite widely panned, but you can get over Kratos' dickbaggery if you just assume him to be the real villain of the story. Play it.
Don't bother with Ascension. It's among the best looking games on the PS3 (I would say it's the best I've seen on the console), but other than that it doesn't really deliver. The story feels like fan fiction, the gameplay is nerfed significantly, a few of the new gameplay mechanics seem rushed and don't see much use, and the level design leads to some scenarios that, if you stop to think about them for even a second, are downright retarded.
If JRPGs are your thing, the FFX/X2 HD remaster gives you two games, one of which is still very good looking and solid gameplay wise, and another which I haven't played. Be prepared for lots of unskippable cutscenes and ridiculous JRPG character designs though. If you can get past that, FFX is a very addictive, sprawling RPG.