Roller Coaster Tycoon Classic was developed by Chris Sawyer, who did the first two games, and then left the games industry for decades, partially because of a disgust with the shift towards violence[0][1]. So in a way, Roller Coaster Tycoon Classic is the first "canon" Roller Coaster Tycoon sequel after the first two games.
Also, the first game was almost completely written in assembly[2]. I don't think one can pull that off without having some really high coding standards, so I'm not surprised that the game runs really well!
[0] https://en.wikipedia.org/wiki/RollerCoaster_Tycoon_Classic (note that it also has just been released on Microsoft Windows and macOS on September 28)
[1] http://www.eurogamer.net/articles/2016-03-03-a-big-interview...