Lynk, it all comes down to whether a company believes that its rights have been infringed, and if so, it will bring a case against the infringers. The question is whether the items were lifted wholesale, or similar items were created, but even that question doesn't really encompass the infringement principle.
For direct copying of assets, well, that's pretty open and shut, and if they did it, then I'm not sure what sort of defense they can apply.
As for similarities, the best example from music has to do with George Harrison's "My Sweet Lord", and the old song "She's so Fine". That was a landmark case for musical infringement.
I've seen screenshots of the game, and I don't think it's a question of similarities. I think they may have lifted resources, and in some cases whole level designs, wholesale from other games.
The question of generic versus specific will probably be decided in a court somewhere.
Edit- there are a bunch of screenshots at this Penny-Arcade thread:
[Steal On] Limbo of the Lost (Grand Theft Everything) - Games and Technology - Penny Arcade Forums