Manon; Die Meistersinger von Nürnberg; Idomeneo

Soprano Anna Netrebko, the fabulous, gutsy, quixotic Russian diva of divas who reduces men to milksops, had top billing in the title role of Manon, the Royal Opera's final new production of the season. But the crowd anointed another star: her tormented lover, the Chevalier des Grieux, sung by the Italian tenor Vittorio Grigolo. When he took his final curtain, the roar of approval stunned him to such an extent that, in a moment of pure "what, me?" operatic bliss, he fell on one knee, beating his breast and pointing at his heart, waiting for the noise to stop. It grew louder.

The 33-year-old, who sang in the Sistine Chapel as a boy chorister, won early support from Pavarotti and has released a hit crossover CD, In the Hands of Love, has it all: a bright, pinging voice, crazy good looks and gym-fit physique of which we saw quite a bit when, shriven and ready for the priesthood, he says hell to all that, throws off his cassock and leaps on a handily situated bed – every church should have one – tempted by Manon, coquette and hussy that she is. The devil wore bling and not much else. Who could resist?

If the enthusiasm of the audience was absolute, the critic, trying to salvage a few shreds of objectivity, has to admit reservations about Grigolo's technique (vocal, that is). He triumphs in impassioned outbursts and short, choppy utterances. He inspires pathos, essential in this French romantic repertoire which, respecting its fervent admirers, we shall resolutely not call soppy. When Massenet awards him long, lyrical lines, however, as in "En fermant les yeux", he peters out and forces a raw, nasal noise that isn't always in tune. Once, or if, these problems are solved, he will be a much-needed new tenor superstar. There are too few around.

Netrebko, finding her own new voice post-motherhood, sounded in scintillating form and looked a million dollars, whether as a matronly young Manon, exposing her thighs (phew) and bouncing on beds in a short nightie, or dressed in candyfloss pink and furs as a kept woman. Antonio Pappano, ROH music director, conducted an energised performance with agile orchestral playing and a delicate bonus prelude at the start of Act V. Not that I'm complaining, but where did this music come from? Was it merely a scene-changing device necessary to this cumbersome staging by the usually reliable Laurent Pelly, who scored such a triumph with La fille du régiment?

The look was belle époque, contemporary with the opera's 1884 premiere. In Chantal Thomas's designs, steps and railings imprisoned the enterprise, from the steep staircase of the inn scene at Amiens, to the lovers' upstairs garret in a Haussmannised Paris, to the ramps and rakes of Acts III and IV. The sexy-religious climax of this opera, you may recall, occurs in the Paris church of Saint-Sulpice, so precisely rendered you quite expected Dan Brown to pop up through the gnomon wearing a cilice. Two intervals and long gaps made for a protracted evening. The ballet was terrible: dancers straight out of Degas's rehearsal room paintings wobbled as if they were, indeed, still in rehearsal. But the star couple sparkled.

Many moments scorched themselves on heart and mind during the six hours of WNO's new Die Meistersinger von Nürnberg, but one burnt fiercest. In Act III, in Richard Jones's deceptively straightforward, fresh, Nazi-free production, the townsfolk of Nuremberg gather for the song contest, whose champion will win the beautiful Eva. Dressed up splendidly, arrayed on a garlanded grandstand, the huge chorus await the cobbler Hans Sachs, revered mastersinger and wise elder statesman, sung by Bryn Terfel.

The Welsh bass-baritone walked on stage, turned his back to the audience and looked up at some 60 fellow countrymen singing their souls out to him, fortissimo. It was as if we had witnessed a private moment between Terfel and his homeland. He may or may not have been, like us, shedding a furtive tear. Inextricably associated with the company and its Millennium Centre home, Terfel had fulfilled a promise: to sing his first Hans Sachs, a career peak, on native soil.

It was also the first Meistersinger in the WNO's 64-year history, and worth the wait. In his inaugural season as music director, the German Lothar Koenigs, a Wagner-lover since childhood, showed his intimate knowledge of the score, safe but gifted hands in a complex musical undertaking. Orchestra and large cast rose to the occasion. Christopher Purves's delicious Beckmesser, with a nice touch of Malvolio, was never needlessly ridiculous. Amanda Roocroft made a tender and convincingly youthful Eva.

Raymond Very as Walther, the young knight, looked the part, which is rarely the case, even if he didn't always sound it. Jones's production, designed by Paul Steinberg and Buki Shiff, roamed successfully between middle ages and near modernity. Via a clever visual coup, involving a frontcloth collage showing great German artists of every creed, Jones offered a generous solution to the thorny matter of Wagner's Teutonic patriotism. WNO is on a high.

As Albert Einstein put it, Idomeneo is the kind of work "even a genius like Mozart could write only once in his life". Yet its complicated performance history has not helped its popularity. In a new production ENO used the Vienna edition, with Arbace's arias cut and Idamante sung by a tenor (Robert Murray) rather than a mezzo. In the English translation, Mozart's Latin gods have been changed to Greeks and the recitative texts have been altered, rather cavalierly. This may sound dry, but it underlines how performances of this opera can differ, with the responsibility placed on interpreters. ENO's covetable new Overture Opera Guide to Idomeneo, one of a definitive series building on the popular guides of the 1980s and 1990s, gives a lucid summary.

Edward Gardner, ENO's music director, showed a natural, fluent grasp of the score, though the orchestral playing was patchy. Emma Bell's Electra had belligerence and flair. Paul Nilon negotiated the emotional ambiguities, and dealt superbly with the vocal athletics, of the king saved from a storm who, as a result, must kill his son. The exchanges between Nilon and Murray are heart-rending.

Visually ENO chose minimal modernism for this maximal, classical work. The director, Katie Mitchell, has updated Crete at the end of the Trojan War to a contemporary boardroom interior surrounded by a turbulent sea (realistically captured in Paule Constable's lighting design). Everything else is extraneous, to put it politely. Couples in evening dress straight out of a Jack Vettriano-painted cliché smooch and swan irrelevantly back and forth in the middle of long arias, which is fine for birthday cards but not for masking Mozart's dark-light masterpiece.