I've just found an interesting project called
Gigalomania. Some guy has re-created Mega-lo-mania, using the original data from the Amiga version of Megalomania, and it runs on PC.
I've played a little of it and it seems pretty cool, though it still needs some work. It runs a bit too fast, some of the in-game features don't work correctly. Example, when a new design idea comes up, you don't get any indication that it's ready to be researched. You just have to keep checking regularly.
The cool thing is it's open source so anyone can tinker with it to get it working correctly. I have no experience with CPP so I can't really do anything with it yet. The makers intent with the game is to add new features to the game. A level editor would be a cool thing. Maybe even a head to head multiplayer mode could be created.