Sure, by its ninth, final season the shows mythology was exhausted, with agents Doggett and Reyes (underappreciated Robert Patrick and Annabeth Gish) retracing Mulder and Scullys steps.
But for completists there are good stand-alone episodes: Burt Reynolds as God in the bizarre Improbable, farewell to The Lone Gunmen in Jump The Shark (a self-aware irony discussed by its writer-producers), and David Duchovnys Mulder reappearing for the last ever episode, The Truth.