Design a circuit from logic gates, flip flops and/or multiplexers
The verilog code you write for FPGAs deals with digital logic. It just sees signals either has a "high" or "low", It does not know any values in between. In your current code you are just comparing between signals on the basis of high and lows. You are interested in "real values", say an analog signal which varies between 0 to 5V, and you want to compare them. What you need is only a set of analog comparators. For example for two signals:





Another way is to plug your analog inputs to ADCs, convert it into digital equivalents. Say for example 10-bit digital values. And feed these digital values to your FPGA. You would need to write a similar verilog code for comparison of these signal vectors and drive outputs accordingly.