This paper presents a detailed complexity study of the existing non-binary LDPC decoding algorithms in order to rigorously compare them from a hardware perspective. The Belief Propagation algorithm is first considered as well as its derivative versions in the frequency and logarithm domains. We then focus on the Extended Min-Sum and its recent simplified version. For each algorithm, the number of operations in an elementary step of the check and variable nodes is determined. Finally we evaluate the interest of the application of the simplified Extended Min-Sum algorithm to a new family of non-binary LDPC codes designed in the framework of the DaVinci project