Synthmaster player free is probably the best free synth out there

I'd have to qualify that as "the best free player you can't program". That's because it gives very little control for tweaking sounds, so you'll rely entirely on add-on patch libraries. By the time you've acquired all of the available libraries, you'll be down a couple hundred bucks and at this point it's no longer a free synth, but a moderately expensive one.
 
However, the add-on sound sets for Synthmaster are outstanding, and individually reasonably cheap.