As in sex, so it is in music: there’s a lot riding on the climax. The celebrated third act trio of Der Rosenkavalier is arguably the most famous orgasm in music – dear reader, can you name a better one? – but time it wrongly and you’ll regret it. There is, however, absolutely nothing regrettable about this A-list cast in the hands of director David McVicar and conductor Edward Gardner. Theirs is the most assured, most riveting Rosenkavalier in this country for years.

Francesca Zambello’s production of Don Giovanni may only be 10 years old, but is already showing signs of decrepitude. Even back in its youth in 2002-3, this staging never had much of a spring in its step, but at least there were some fantastic casts to compensate. Bryn Terfel, Anna Netrebko, Simon Keenlyside and Erwin Schrott have all taken their turn here, but even with Gerald Finley returning in the title role there’s little the current incumbents can do to do rescue this aged and confused attempt at a seduction.

It’s the pace that takes getting used to in a Baroque opera. Five words in the libretto can easily take up five minutes to sing, and Handel’s music is often disconcertingly jaunty, even when tragic events are unfolding. Tim Albery has also directed Opera North’s current Madam Butterfly revival, a thrillingly cinematic, fast-moving production. His Giulio Cesare is judiciously pruned, with a total running time of about three hours. The cuts prevent any sense of stasis; what’s remarkable is just how much entertainment Handel’s imperial epic provides.

Two precisely imagined dream-visions bookend a cornucopia on the musical front. I’ll start with the deadly but save the apparently frivolous for the top slot. Christopher Alden’s pitiless exiling of Britten’s A Midsummer Night’s Dream from Elizabethan wood to 1960s school block was to opera what Lars von Trier’s Melancholia was to film: audience-sundering, often alienating, sometimes enticing, but very much its own consistent world. Its splendid cast and conductor Leo Hussain worked as one to enhance the paradoxes of its terrible beauty.

The Barbican has always led the way in London in international theatre programming. The year there ended on a high, with Thomas Ostermeier’s Hamlet from the Schaubühne laying down new markers for transgressive commitment. I was sceptical about it when I saw the Berlin première in 2008, and our own critic was not, commendably enough, in a mood to be fooled around with. Yet a production which stages, so stylistically, terror, insanity and loathing (all in Shakespeare) with six actors straining every sinew without entirely ridiculing the play has to be respected.

While I'm still learning to disentangle my mezzo from my Meistersinger, I enjoyed a lot of the opera on offer in London this year, especially at English National Opera. Parsifal was perfect and Rameau's Castor and Pollux, while probably a little too Germanic in direction with its dancing amputated legs and unerotic nudity, was wonderfully sung. I especially enjoyed the premiere of Nico Muhly's Two Boys, whose internet-era set design suited its perverse modern "love" story.

A young chap from Elsewhere woos an alderman's daughter: not Dick Whittington in panto London, but Wagner's Walther von Stolzing in an unseasonal Nuremberg. No one is going to mind the solstitial disjunction - celebrating midsummer revels in the dead of winter - when this great saga of art and society is buoyed up by Antonio Pappano's lovingly prepared conducting, a good cast, lusty chorus and colourful costumes.

It is unusual in art for collaborators to be of equal star-wattage. The pairing of Benjamin Britten and WH Auden was one such. Another, much longer-lasting, was Stravinsky and Balanchine, a partnership of equals that endured for nearly half a century. More recently, Antony Gormley has worked with both Akram Khan and Sidi Larbi Cherkaoui, to great effect. Can Turnage, McGregor and Wallinger replicate these? This has been the question.

Who is more likely to be an operatic creature of flesh and blood: Puccini's young diva, unexpectedly caught up in the infernal machine of a lustful tyrant, or Tchaikovsky's teenager impetuously pouring out her soul in a love letter to a man she's just fallen for? Usually, you'd go for Tatyana over Tosca every time. At ENO it's currently the other way round.

Theatregoers may be disappointed to read on and discover I mean Otto Nicolai's Die lustigen Weiber von Windsor, the only 19th-century Shakespeare-based opera in the German language to hold the stage. Which it did, and not just in Germany, until the arrival of Verdi's infinitely superior Falstaff. Is this that rare thing, German comedy in music between Beethoven's Eighth Symphony and Richard Strauss's Till Eulenspiegel that's actually funny? Not really; Wagner's Die Meistersinger stands alone.