Magog's power was never really defined too well in any of his appearances, as I recall. It seemed Ross was more intent on clearly expressing what an analogy of the bad-ass 90's Magog was that he forgot to do this, although maybe that was the point - Given bunches of heroes and the like seemed to get powerboosts conviniently timed so they could defeat a stronger enemy - at least, in the independants, anyway.
As it was, Magog didn't even seem capable of harming Superman during Kingdom Come, and whilst that Superman's ten years beyond the version in the current books, I doubt he could do that much.
Personally, I always thought Magog was the comic book embodiment of the idea of 'all mouth, no trousers'.