From my (very) Limited knowledge of the hardware of both systems, apart from speed, the 8-Bit's lack of a way of tripplexing the sprites width-wise (e.g. three planes in "Combat", three logs in "Pitfall!") would be a stumbling block, as well as a straight-forward 40-byte wide "playfield" register.
As Keetah says, porting is more obvious (see Phaeron's port of "David's Midnight Magic" from the 2600 - there are others too). And of course if the source code is available, that would be more useful.
Perversely, I'd like to see a more 2600-a-like version of Pitfall! for the A8 than the existing version, but I guess that's just because it's the version I grew up with