Singularity is a ripoff of several "great" games.
The best thing about Singularity is its art style, it's not amazing, but it's nice to look at and I think the developers could have done much worse. It controls nicely, and many of the guns are fun to use. The pacing is great, and you never feel like you're tired of shooting things/solving puzzles/exploring. I felt no reason to go back and play through the story again after I had beaten it. What I don't like is that it does nothing special and the multiplayer is completely dead on PS3. For this alone it's not worth paying full price for.
Again, singularity doesn't do anything "wrong" but everything about it is extremely average for the time. With no online multiplayer, I would rent or wait for a price drop.