I think drawing the conclusion that an aircraft is inherently reliable because there's more of them being made is something of a stretch.
Having said that, it can be said that manufacturers of aircraft have now adopted principles that maximise the reliability of the engines they choose to install.
In other words, I don't think engine "reliability" is much of a distinction nowadays.
Cost of operation however, is entirely a different matter for engines.
If reliability is a big thing for you, there are many other components that you may wish to consider.