Halo 3: ODST
The fact that they called it Halo 3 colon blah rather than Halo 4 should tell you everything you need to know about the game. It's more Halo 3, with the same gameplay, weapons, vehicles, and story. The plot, drop troops in occupied New Mombasa, basically amounts to a footnote in the Halo mythology. And playing as a non-superpowered helljumper is no different than playing as a SPARTAN. Sure, you don't have shields, but your character is still pretty damn tough on normal difficulty.
It's also really, really short. To compensate, the developers included a second disk with Halo 3 multiplayer, but there are only a few new maps.
There's no way in hell this game is worth $60, but hardcore Halo fans will find more of what they enjoy.