Just returned from a recent holiday on which my son and I were discussing how awesome it would be to have a Rollercoaster Tycoon style game set in a ski resort. You would build lifts and decide where the pistes would go, and AI skiers would start using it. You could have skiers of different abilities, including daredevil off-pisters who would try out interesting routes and sometimes have accidents etc. Add in a first-person view so you can ski the runs yourself, and MP so you can invite other people to take part, with races and such like; include weather simulations and occasional avalanches - I think it could be an amazing game for the kind of person who likes these kinds of sims (not me - I don't have the patience!)
Yep, it was called... Ski Resort Tycoon
It's an old one, and from what i remember from my short playthrough, not a very good game compared to other tycoons that were popular back then.
And there's also some more recent game on steam: http://store.steampowered.com/app/346240/