Wagner: Greatest thing ever, or personification of everything wrong about Germany and German culture?
There's also Wagner or Verdi?, since their approach to music and their general philosophies were pretty much the exact opposite of one another; and personally they couldn't stand each other. These facts, plus that they were born in the same year inspires festivals where both are celebrated.
Original language or translation?
This one has petered out a little in the last decade or so, with all but the most ardent die-hards considering the surtitling machine to be an acceptable compromise.
Spoken or sung recitatives?
Classical or Modern opera?
Baroque Opera - Yay or Nay?
Traditional or modernized production?
Maria Callas or Renata Tebaldi?
Mario Lanza or Jussi Björling?
Giuseppe diStefano (light and sweet) or Franco Corelli (massively, spectacularly heroic)?
Straight-ahead singing or vocal acting? Tito Gobbi (baritone) had such a weird voice (and a pea-soup Venetian accent) coupled with superb dramatic skills that he was often regarded as a vocal actor rather than an "opera singer" per se, even though he sang dozens of operatic roles. Maria Callas with her Greek klarino-like voice is sometimes classed as this too.
Unless you have a death-wish, do not ever even imply that The Phantom of the Opera is an Opera in front of opera fans. You will be swiftly struck down.
Do not ever say that "popera" singers such as Andrea Bocellinote Although he studied with the renowned Franco Corelli or, dear God, Charlotte Church, are opera singers. An opera fan's pet peeve, Berserk Button to a few die-hards.
Hotter and Sexier: As with theatre in general, there has been a move in recent years to sex up the form, with productions featuring sexual explicitness and actual or implied nudity. Recent examples include Thomas Adès' 1995 piece Powder Her Face, which included a scene of simulated fellatio among other implied sexual acts, and Anna Nicole, an adult-oriented 2011 opera by Mark-Anthony Turnage that profiled the life of Playboy Playmate Anna Nicole Smith.
Narm Charm: Yes, Opera fans are fully aware that the entire genre is excessive and overwrought and hammy and campy and melodramatic and frankly a little ridiculous. What's not to like?
The 1987 Dario Argento film:
Complete Monster: Inspector Alan Santini was a Serial Killer in a relationship with Betty's mother. He would tie up women and kill them while she watched. After she pressured him to do it more often, he got fed up with her ordering him and killed her as well. Deciding to make Betty his new target, Santini stalks her at the opera house she is performing at and murders people in front of her after tying her up and forcing her eyes open so she sees everything. He kills three ravens during his murder spree, and eventually sets a room on fire to kill Betty. When he survives, he pursues her all the way to the Swiss Alps to make her his.