Which font is the best to make a résumé look equally good on all operating systems?
Why not convert the resume to a PDF so that it looks the same across the different OS's?
Sadly and boringly Times New Roman for printed / pdf documents.
Or are you asking about a font for web delivery? It's hard to tell with the lack of any real information in your question.
If you want to be completely platform neutral then you should format it in plain text and wrap it at 80 columns. Otherwise, even if you end up using Times New Roman which is available on nearly every platform but put it in a Word document, you'll be restricted.
The Microsoft Core Fonts like Arial, Verdana, Tahoma and Times New Roman are usually available on most platforms, but there's no guarantee that any font is available on any platform. The best thing to do is use a document format that preserves font information such as PDF, which is an open-spec file format with at least primitive viewers available on the most widely used platforms.