Real Madrid, Barcelona, Liverpool, Ajax or AC Milan? As Zinedine Zidane brings curtain down on end of an era, we ask: which is greatest-ever team?

THREE consecutive Champions Leagues titles in this day-and-age surely qualifies you as the greatest side ever, right?

Before the rebranding in 1992, when only league-winners were involved, the top teams would often find a much easier path to the final, allowing for more successive victories.

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However, with the biggest now leagues having up to four qualifiers nowadays, it's almost impossible to avoid facing one or more of elite en route to the final, making Real Madrid's achievement even more incredible.

And yet no one has ever been blown away by them. Under Zinedine Zidane, they would always do just enough.

But what is it that actually makes you the best-ever? Trophies won? European dominance? Maintaining a high level both domestically and on the continent over a long period of time?

Or is it simply changing the game forever? Here, we rank the seven greatest sides of all-time.

7. Liverpool, 1976-81

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Bill Shankly had led the Reds from the second tier, before his assistant Bob Paisley carried on his work to make them Europe's most-dominant side.

Like Real Madrid, Liverpool have an affinity with continent's most prestigious competition and English football has never since had a side as imposing in Europe for such a sustained period.

At a time where only champions qualified for the European Cup, the Anfield giants would win the competition three times in five years.

In Kevin Keegan and John Toshack in attack, Paisley had perfected the big man-little man combination to devastating effect.

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6. Real Madrid, 2014-18

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"Results don't lie" they say, and yet somehow, with this side, it is difficult to believe them.

Real Madrid have won the past three editions of the Champions League without ever truly being the outstanding side in Europe.

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Zidane has drilled his players to just get the job done and they always seem to do it — without ever blowing their opposition away.

Trophy-wise, this side is simply sensational, but their impact on the game is actually quite minimal.

5. Inter Milan, 1962-67

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Helenio Herrera created Il Grande Inter, which won back-to-back European Cups in 1964 and 1965.

The legendary Argentinian manager applied a modified version of the Catenaccio system in which he used a fifth defender to create a 5-3-2 formation, which allowed for greater counterattacking flexibility.

Inter made Luis Suarez — the only Spaniard to ever win the Ballon d'Or — the first £100,000 player in 1960 and he and Sandro Mazzola were key to their success.

Herrera also won three Serie A titles in four years as well a two Intercontinental Cups.

4. Real Madrid, 1955-60

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Five triumphs in the first five editions of the European Cup got the competition going at a time when it was met with scepticism by so many across the continent.

This side would blow anyone away, winning finals by scores rarely seen in today's game.

In Alfredo Di Stefano and Ferenc Puskas they had one of the most lethal strike partnerships in the competition's history.

While they won more than anyone, what holds them back is that they didn't change the game, their sole focus was dominating on the continent — much like the current side.

3. Barcelona, 2008-11

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Two Champions League triumphs, three successive La Liga titles and Treble boot. All in just three years.

But Pep Guardiola's influence runs deeper than simply winning silverware, as he brought about a new style built on short passes and movement in order to maintain possession known as Tiki-taka.

The new brand of football was copied all over the world and was integral to Spain's international dominance over the same period.

In 2009, Barcelona won six major trophies — La Liga, Copa del Rey, Champions League, Supercopa de Espana, Uefa Super Cup and Fifa Club World — a 12-month haul which has never been matched.

2. AC Milan, 1987-91

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Historically, Italian football is very tactical, with strong defences reigning supreme, but Sacchi countered this in groundbreaking fashion.

His Milan side played with a high intensity and high line, which allowed them to control the middle of the pitch by ensuring the distance between attack and defence was as short as possible.

It was the first example of such intense high pressing, which many claim led the way for Guardiola to perfect it at Barcelona.

Led also by the Dutch trio of Frank Rijkaard, Ruud Gullit and Marco van Basten, they won back-to-back European Cups 1989 and 1990.

1. Ajax, 1970-73

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Though the foundations for the Total Football played by this side were actually reportedly laid as early as the 1910s, it was through the majesty of Johan Cruyff that this style would be perfected.

Managed Rinus Michels, who played under the art's alleged founder Jack Reynolds at Ajax, implemented this dynamic whereby every outfield player could play in any position.

The style was then used by the Dutch national side which dazzled its way to successive World Cup finals in 1974 and 1978.

Ajax would win three European Cups, two league titles and the 1972 Treble in that three-year period.