I’m thankful to see that I can give my first answer without having to explain further:
My favorite opera is any one that Anna Russell has summarized.
I’ve never really watched or listened to opera, except that I love Gilbert & Sullivan. HMS Pinafore is my favorite, but I’ve only seen The Mikado live.
…and he immediately falls in love with her because she’s the first woman he’s ever seen that he’s not related to…
…the ring. Remember the Ring?
A sort of aquatic Andrews Sisters…and they sing this little song. I won’t translate it, because it doesn’t mean anything.
And I thought I was the only one…and Shaw says it’s stuff. 
The Tales of Hoffmann of Offenbach gets a bad rap, I think. I love it! Not my favorite, though…
I think that might be Elektra (Richard Strauss) or, predictable, The Marriage of Figaro. Has anyone seen the Gyldenbourne production with Gerald Finley and Renee Fleming as the Countess, with Sir Colin Davis at helm? That is just otherworldly, it’s so good. Gerald Finley is just…blistering as Figaro, and if Renee Fleming doesn’t break your heart at the start of Act II…well then try the closing redemption scene just before the last little big ensemble number! That never fails to reduce me to a puddle of emotional jelly.
Is it illegal to have runner ups? Virgil Thomson’s Four Saints in Three Acts is horribly underrated and underperformed, IMHO.
ULP- after writing all that, I realize my REAL personal favorite is Benjamin Britten’s The Turn of the Screw, based on the novel of Henry James. Creepy and oftentimes depraved music, exquisitely written as always with Britten. I think it is possibly the only opera that is truly horrific and chilling in a horror movie give-you-the-creeps-in-the-still-of-night kind of chilling. Love it.