As others have said, a clone could be possible, not a direct port. However I think that you're underestimating the amount of effort needed to create a game like that (even one now as relatively old as the original Sims). I'm no programmer myself, but the advice everyone seems to give is to start small: write a few trivial apps, then a game of noughts-and-crosses, then chess, then a simple turn-based strategy game etc.
You might want to have a little look into the SDL library - if you were to write a game with that then it would be easily portable onto the Amiga/PC/anything. Here's my experience: I wrote a nice little isometric engine in C++ and SDL that could do smooth-scrolling, multiple heights, seperate user-placable buildings etc and looked identical to C&C: Red Alert. It ported onto the Amiga with no real modifications, which was very satisfying. The aim was to use it as the basis of a C&C-type RTS game, however that was way to big for a first project, and the code's been in storage for a year or so now. On the other hand, I'd never used anything other than AMOS and Visual BASIC before, having always assumed C/C++ the realm of professionals. After reading a book a book ("teach yourself C++ in 24 hours") it turned out to be a lot easier going than I'd imagined at first.
BTW I don't know how realistic it would be to get something like The Sims working nicely under AGA. While it can display 256 colours, it's dog-slow when doing that.
