The scientific community is focused on the development of inexpensive and high-performing membrane materials for proton exchange membrane (PEM) fuel cells (FCs). The major approach to reducing the cost of FCs, which is crucial for the widespread acceptance of FCs as energy sources for various practical applications, is reducing the cost of the membrane. Efforts are being made in the development of advanced polymeric materials, which will satisfy the technical and economic demands of the consumers. Because most alternative membranes are outperformed by Nafion membranes over an entire set of important properties, it may be worthwhile to compromise on certain parameters to develop alternative specialized membranes. This review presents the properties (mainly conductivity and chemical and mechanical stability) of modern solid polymer electrolytes (SPEs) for PEM FCs.