I see a lot of people on this forum talking about graphics, custom scenery, and a spline system, among other things. However, for me, my favorite part of the RollerCoaster Tycoon series was being the tycoon. I loved the financial management aspect of the games. Everything from deciding where to put shops, where to set prices, when to market, and how many employees to hire. I just wanted to remind the developers that this is what separates RollerCoaster Tycoon from an architect's tool, and makes it into an actual game.