My device is Samsung Galaxy S5 with Android lollipop.
Some games run on a landscape mode and the top-side becomes left-hand side and bottom becomes right-hand side. Can I change this so that top goes right and bottom goes left? I don't want to rotate my phone every single time I run these apps.
You can easily achieve this by automation. I prefer MacroDroid Being easy to learn and free
To understand how MacroDroid works and the settings required for your Android version, see my answer
Your macro would look like this and you can tweak as you like
Trigger: Application Launched / Closed → Select your application
Action: Force Screen Rotation →Force Landscape (or) Force Landscape 180 (Screen shot below shows possible options)
Constraints: None
