We propose a method to synthesize a parameterized infinite-state system that can be instantiated for different parameter values. The specification is given in a parameterized temporal logic that allows for data variables as well as parameters that encode properties of the environment. Our synthesis method runs in a counterexample-guided loop consisting of four steps: (1) we synthesize concrete systems for some small parameter instantiations using existing techniques. (2) We generalize the concrete systems into a parameterized program. (3) We create a proof candidate consisting of an invariant and a ranking function. (4) We check the proof candidate for consistency with the program. If the proof succeeds, the parameterized program is valid. Otherwise, we identify a parameter value for which it fails and add a new concrete instance to step one. To generalize programs and create proof candidates, we use a combination of anti-unification and syntax-guided synthesis to express the differences between the programs as a function of the parameters. We evaluate our approach on new examples and examples from the literature that are manually parameterized.