While attempting to install 'RetroPie' on to my RaspberryPi2 : Model B, running Raspbian Jessie + Pixel Desktop the following error was being reporting when starting 'emulationstation' from the terminal server.

lvl0: Error creating SDL window!
Could not get EGL display
lvl0: Renderer failed to initialize!
lvl0: Window failed to initialize!

After several hours reading many articles and trying many different installations, I found the answer was to simply boot to the command line, by disabling the Pixel Desktop within 'raspi-config'.

 Once rebooted, 'emulationstation' works as expected.