Since Cristiano Ronaldo arrived in Madrid for £80million in 2009, it has been the eternal question: who is better out of him and Lionel Messi?
More than five years later we still don't know, with a preference for one or the other largely coming down to personal opinion.
After Cristiano Ronaldo scored a 23rd La Liga hat-trick on Saturday night Messi responded in the way they have been doing to each other throughout their careers - by scoring a hat-trick of his own, his third in four games.
In fact, statistics provided by WhoScored (click image above to enlarge) show that the rivalry is even closer than one might suspect - Ronaldo and Messi, undoubtedly the world's two best players, share almost identical statistics across the board.
Cristiano Ronaldo arrived for a then-world record fee and immediately took La Liga by storm, scoring 33 goals in 35 matches in his first season in white.
But back then, Messi was the undisputed king of world football, and scored 42 goals in La Liga and the Champions League as Barcelona won the Spanish crown.
Gradually, however, Ronaldo has improved his game to reach the level of his fierce rival and the stats bear that out, eerily so.
El Clasico: Memorable moments and why Real Madrid vs Barcelona is so special
El Clasico: Memorable moments and why Real Madrid vs Barcelona is so special
1/9 RAMOS DROPS THE CUP
When Real Madrid beat Barcelona 1-0 in the Copa del Rey final in the 2010/11 season, it was the first time they had beaten their hated rivals since 2008. Naturally, the players went wild in celebration. None more than Sergio Ramos, who dropped the trophy from the team's open top bus during a victory parade through Madrid's city centre.
2/9 MESSI V RONALDO
This fixture has been billed as the battle between the two best players in the world since Cristiano Ronaldo signed for Real Madrid in 2009. It hasn't failed to deliver either. For a long time Messi was considered marginally the better of the two, but at the start of 2014, Ronaldo won the Ballon d'Or, ending Messi's four year run of successes.
3/9 CLASSIC MATCH: 1936 Real Madrid 2-1 Barcelona
The two teams have long represented the struggle between nationalists and republicans that led to the Spanish civil war, and as fate would have it, the last game before war broke out was between Real Madrid and Barcelona, in the final of the Copa del Rey. The game has gone down in Spanish folklore for the amazing save that Spanish goalkeeping legend Ricardo Zamora (pictured) made in the last minute of the game to prevent Barcelona from equalising.
4/9 POLITICAL DIVISIONS
The rivalry goes beyond what happens on the pitch. Barcelona see themselves as representing the region of Catalonia, which seeks independence from Spain. Real Madrid, meanwhile, are seen as representing Spanish nationalism, centralisation and loyalty to the King. A Barcelona win is often reported by the press as Catalonia getting one over the establishment, while a Real Madrid victory is seen as the capital asserting its authority.
5/9 MUTUAL APPRECIATION
While El Clasico is rightly described as one of the fiercest rivalries in world football, there have been times when fans have shown great praise for the opposing team. Andres Iniesta received a surprise standing ovation from the Bernabéu when he was substituted after a superb performance. Before that, Ronaldinho was applauded by Madrid fans in 2005 when he scored two brilliant goals in a 3-0 win for Barcelona, while the late Lawrie Cunningham received a similar amount of praise from the Nou Camp after helping Real Madrid to a 2-0 win over Barcelona in 1980. Even Cristiano Ronaldo, in more recent years, has been acknowledged by Barcelona fans.
6/9 A NATIONWIDE RIVALRY
The ideological and political clash that exists between the two sides has the power to not only divide the supporters of these two clubs but Spain as a whole. Many fans of other La Liga clubs have a clear preference for Madrid or Barcelona based on their ideological leanings and will watch El Clasico with as much interest as when they watch their own team.
7/9 THE TWO GIANTS OF SPAIN
Real Madrid and Barcelona are far and away the most successful and best supported teams in Spain. Real Madrid have won 32 league titles, while Barcelona have 22. Only in more recent years has the country's third most successful club, Atlético Madrid, challenged their authority. Barcelona and Real are also the only two Spanish teams to have won the Europe's biggest prize, with a total of 14 European Cups between them.
8/9 PLAYERS WHO CROSSED THE DIVIDE
The rivalry has become more intense due to star players making controversial moves from Barcelona to the Spanish capital. The most famous cases are Luis Figo (pictured), who had a pig's head thrown at him on his return to the Nou Camp in a Madrid shirt, and Michael Laudrup, who joined Real Madrid from Barcelona in 1994 and immediately inspired his new club to a league title, ending four years of Barcelona domination. Other players who have played for both teams include Ronaldo, Luis Enrique, Samuel Eto'o, Bernd Schuster and Javier Saviola.
9/9 VIOLENT SCENES
Tensions often reach boiling point when these two clubs meet. In a match in 1990 Hristo Stoichkov earned himself a two month ban when he stamped on the ankle of referee Ildefonso Urizar Azpitarte, who had just sent off manager Johan Cruyff for dissent. After a recent Supercopa match at the Camp Nou, which Barcelona won 3-2, a scuffle broke out between the two teams' coaching stuff, ending with José Mourinho poking Barcelona's assistant manager Tito Villanova in the eye.
Since 2009 - counting La Liga and the Champions League only, not the Copa del Rey or other competitions - Cristiano Ronaldo has played 234 games, scoring 256 goals, while Messi has played five more games and scored three more goals (259 in 239); both astounding totals
With Ronaldo in the staring line-up Real Madrid have fared slightly better than Barcelona with Messi, but only just.
Real Madrid have won just shy of 77 per cent of games where the Portuguese has started and Barcelona just shy of 74 per cent, with each team losing around about 10 per cent of their matches when the two players play.
The way the goals have come is where the pair see their main difference.
Though the pair have netted a similar amount from inside (219 for Messi and 214 for Ronaldo) and outside of the box (40 for Messi and 42 for Ronaldo), the manner in which they have scored their goals highlights the differences.
Ronaldo has scored 29 headers since 2009 compared to just 10 for Messi, while Ronaldo has proved to be much more deadly from set-pieces, scoring 49 penalties and 23 free-kicks, compared to just 32 penalties and 13 free-kicks for Messi.
Messi scores the majority of his goals with his magical left-foot - 207 of the 259 - while Ronaldo has scored only 182 of his goals with his thunderous right-foot.
The pair's WhoScored ratings over the period are also near-identical, 8.67 for Messi compared to just 8.31 for Ronaldo.
There is one area where Messi has been more successful than his opposite number: trohpies.
In those five seasons, Messi, part of arguably the greatest club team of all time, has won La Liga three times compared to just one for Ronaldo in 2011-12.
However, the tide could be turning in Ronaldo's favour. Winning La Decima made it 1-1 in Champions League wins since 2009 and the Copa del Rey triumph made it two for Ronaldo to Messi's one.
With Real Madrid currently top of La Liga and victorious in El Clasico in October, as well as being the favourite to win a second successive Ballon d'Or, it may be that Ronaldo is edging ahead in the head-to-head.
But as Messi showed at the weekend, responding to Ronaldo's hat-trick with one of his own, there is still a long way to go in this great rivalry.Reuse content