Most classical sampler discs are 'performer-proof', i.e. you can easily enjoy the composers' musical creations without being distracted by any flawed musicianship on the part of the performers.

However, with opera sampler or compilation discs, especially those issued from a young label with no roster of famous singers in its stable, a lot of things can go wrong.

IME listening to these discs is like being serenaded by nameless ghouls in the dark.   

Best avoid your entry into the wonderful world of opera via this route.