It depends... what's the value and voltage rating, and in what circuit is it used? Mylar caps have very low leakage and moderate dielectric soakage... just to list one example, if it's a power supply bypass, a disc ceramic would work. However, ceramics are quite nonlinear with voltage, so they would be a poor choice in an audio stage or other linear amplifier.
Polypropylene caps are more expensive and bulkier, and generally max out at lower capacitance than Mylar, but would electrically be at least as good. You probably don't want an electrolytic if the original cap was Mylar since they have large capacitance values, higher leakage, wide tolerances, etc.