The dream - or obsession - was realised last night as they overcame cross-town rivals Atletico 4-1 in extra-time in the Champions League final. They needed a late, late comeback against a team who emerge with huge credit from a fairytale season.
Atletico started with Diego Costa, who had aggravated a hamstring injury just a week before but, following some exotic treatment involving horse placents, was deemed fit. The gamble, and it was still a gamble, backfired. After nine minutes, the Spain internationalist limped off to make way for Adrian, delivering in the process a tactical body blow for Atletico.
Simeone's reshuffle meant the eternally inconsistent Adrian, the uber-decorated (but, as far as his Atletico stint is concerned, distinctly sub-par) David Villa and the blue-collar Raul Garcia (more of a super-sub who was, nevertheless, the side's second top scorer) were now charged with leading the counter.
Yet Real Madrid struggled to capitalise. Gareth Bale and Cristiano Ronaldo were innocuous. An errant pass from Tiago gifted Bale a clear run at Thibaut Courtois's goal, but the finish that followed his scything run trickled wide of the far post.
Miss at one end, get punished at the other; the old footballing law struck again in the 35th minute. A half-cleared corner was sent back in by Juanfran and Diego Godin climbed over Sami Khedira to head goalward, the ball looping over a frantic and stranded Iker Casillas.
It was the kind of mistake you don't expect from the man they call "San Iker". But it was also the sort of scrambled goal you do expect from Atletico this year and it seemed fitting that Godin, one of many unsung cogs in Diego Simeone's machine, should be rewarded.
At half-time came a telling moment. The Real Madrid fans began chanting "Si se puede!" ("Yes, we can!") which, before it was co-opted by Bob the Builder and Barack Obama, was the traditional underdog ditty of the South American under-classes. It was ironic, but it also illustrated how this Atletico team was putting fear in Madrid hearts.
Ancelotti looked befuddled. Ronaldo was AWOL, Bale drifted in and out and Karim Benzema was either unfit or shell-shocked. Further back, Khedira simply couldn't fill Xabi Alonso's shoes.
He had to gamble and, just before the hour mark, he did. On came Marcelo and Isco for Fabio Coentrao and Khedira. Real Madrid's vice slowly tightened.
And deep in injury-time they were rewarded. Sergio Ramos, the emotional leader on the night and the hero of the semi-final demolition of Bayern, nodded the perfect header past Courtois.
One-one. Extra-time. And the ghosts of 40 years ago reared their heads. In 1974, Atletico, then as now coached by an Argentine, gave up a last-second equaliser to Bayern Munich in a European Cup final and lost the replay 4-0.
Those spectres needed to be exorcised, but they weren't. With 10 minutes to go and both sides exhausted, Angel Di Maria, seemingly the only man with any juice left, burst down the left flank, turned two defenders inside out and unleashed a vicious finish which the outstanding Courtois could only deflect into the air.
On rushed Bale, who headed it past the goal-line. Marcelo sealed it when he made it 3-1 moments later. Simeone acknowledged it by going over to the Atletico fans and applauding them. A classy move by a class act whose feats this season won't be forgotten. Ronaldo won - and converted - a penalty to make it 4-1. Giving it was as needless as his shirtless celebration. This was not his night, perhaps he could have left the stage to others.
The hope for Atletico is that it won't be another 40 years before they return to a Champions League final. The fear, given the way the game is going, is that it might be longer.
As for Real, they have made history once again. And, for all the cash lavished on the hunt for "La Decima" - a billion Euros in 12 years by some estimates - it wasn't the megastars who brought it home, but resolute centre-back Ramos and an under-appreciated winger reinvented by Ancelotti as an attacking midfielder, Di Maria.