Maybe this is the wrong place to ask, but what platform would be the most suited to create a similar type of game as newlife? It has to be difficult since this guy is still in business.
I've considered creating a similar game myself but wouldnt really know where to start when it comes to creating this type of GUI and whatnot
If you don't know where to start, then don't bother. Making a game like this is a programming task more so than a writing task. If you really are interested, take a look at C# (.NET) or NodeJS. For C# use Unity or WPF/WindowsForms for streamlining frontend. For Node it's all HTML which has more tools than you would ever need (Bootstrap, Foundation, Bulma, React, Angular, etc.)
.NET has incredibly useful tools and C# is a very robust language with strict typing and an easy to understand object based paradigm. JS on the other hand is extremely hacky from its roots as a purely front end tool, but ECMAScript 6 has saved it somewhat and React has smoothed the process further enabling you to deploy an application in practically no time at all.
They are both platform agnostic (C# only with Unity) and can be deployed on both desktop and web (and mobile for that matter), so you don't have to worry about that. Happy coding.