Are you kidding? Think about all the skilled contributors that currently work on emulators, do you not think that some of them would switch to working on re-compiling games? And I agree there are probably weird platforms that it wouldn't be easy for, but anything x86 is going to be much more trivial. I mean, someone was even reverse-engineering Super Mario 64, re-coding the entire game. The original source code and ability to use the code without getting sued would make things so much easier. Yeah, not every game would be done, but the big titles would be.

As far as emulating the rest, access to the source code would make it far, far simpler to figure out compatibility issues and make sure that every game is actually playable.