Native port - an oxymoron methinks.
Well, "native" in the sense that it doesn't rely on a translation layer, as I mentioned above. The same also applies to Linux "ports" which use Cedega, an earlier predecessor to Cider. Yes, COD4 does perform horribly even on Intel systems which are comfortably above the system requirements, but anyone who was a Mac gamer during the PPC days will tell you that poor performance was what was often seen for a lot of native Mac ports.
FWIW, from what I hear on the IMG forums, the port of Bioshock performs pretty well.
For people who really care about MW2, CodeWeavers is working on official support for it (which I guess they can concentrate on now after working to officially support Left 4 Dead 2). They already have rough support for MW2 in CrossOver Games 8.1.
AppShelf: MacHeist 3 Loot
AppShelf: nanoBundle 1
Check Reciept Page for nanoBundle 2 AppShelf Files.