I played through Darksiders about a week ago, had a lot of fun with it, towards the end I had found most of the collectibles so I used a guide to find the rest of them.
And then just the other night I sat down, started and finished Singularity in one sitting. It was fun, pretty standard FPS stuff, the time manipulation device is fun to play around with. Though i think the game was geared more to be played on a console, I played it on normal difficulty and just felt it was way too easy. The assault rifle just felt over powered, you don't even need to use your other abilities really. Anyhow it's probably more worth looking into at a lower price point.