Several of the maps from halo 1 make an appearance in halo 2, but Bungy modified them all at least a little bit. Warlock is like wizard, coag is obviously like blood gulch, and beaver creak is pretty close the battle creak (the closest remake, IMO).

But would it have been so bad to simply port over the old stuff? I personally loved sidewinder, for example. Would anyone here complain if they ported it over? I mean... we have someone making a port of Chiron TL34. And someone else making a port of blood gulch, despite the fact that it was "remade" into coagulation. (i still miss the old one).