The correct "Input Termination" option to use is "DIFFERENTIAL"
The resulting variable is added to the qsf file.
set_instance_assignment -name INPUT_TERMINATION DIFFERENTIAL -to <input_pin>
Check the respective device handbook to verify if differential termination is supported for the device family you are using.
When using the ALTLVDS megafunction for dedicated SERDES the Quartus® II fitter will automatically assign the LVDS standard for the I/O pins, however you will need to make the differential termination assignment for the LVDS receivers.