Despite Real Madrid and Barcelona splashing out in excess of €150 million onGareth Bale and Neymar, respectively, it is two extremely familiar La Liga foes who are back to their old ways—Cristiano Ronaldo and Lionel Messi.
Although the 2013/14 season remains in its infancy, both superstars are wreaking havoc and chaos amongst opposition defences, both domestically and abroad.
Last season, Messi picked up his fourth successive Ballon d'Or after he broke Gerd Muller's 40-year-old calendar-year scoring record with an astounding 91 goals in 69 games during 2012.
Ronaldo set about in his relentless quest to wrestle football's most prestigious individual honour away from the Argentine, with a hugely impressive 46 goals in 46 La Liga and Champions League matches last season.
Sourced from ESPN
No doubt a brilliant accomplishment but, yet again, Ronaldo found himself in Messi's shadow as Barcelona's No. 10, hit 54 goals in 43 games—with 17 assists thrown in for good measure—in the same competitions.
More importantly the above table shows a three-season comparison between the pair. Judging on the statistics alone, it is hard not to argue that Messi is the superior player—having scored more goals in fewer games and possessing a better goal conversion percentage (notwithstanding the numerous trophies Barcelona have accumulated).
Squawka.com—Messi vs Ronaldo goal conversion in La Liga during this season
This season, the two have started very strongly. Ronaldo has netted six goals in six La Liga appearances, plus a hat-trick in his sole Champions League outing. Messi, not one to be outdone, matched the Portuguese's European feat and has scored seven goals in five games domestically.
Furthermore, the above graph demonstrates that Messi's stronger conversion rate in La Liga this season, ensures the trend of the last three years remains consistent and shows no signs of diminishing. 
Through statistics sourced from Transfermarkt.com, so far this season Messi has averaged a goal in every 51 minutes in La Liga and Champions League compared to Ronaldo's one every 70 minutes.
Ronaldo vs Messi 2013/14 season
With the official Ballon d’Or announcement in January plus a World Cup to look forward to, the unplayable Portuguese and Argentine will continue to flourish. 
This relentless and sustained rivalry is one not seen in football for many years, possibly since the days of Ruud van Nistelrooy and Thierry Henry when Arsenal andManchester United regularly locked horns for the Premier League title.
Between the two, they enjoyed a stranglehold of England's player of the year awards for three consecutive seasons commencing in 2001/02. Like their La Liga peers, they also battled for the honour of top scorer—an award which Henry would win four times in five seasons (2001/02 and 2005/06).
Although Franck Ribery won the European Footballer of the Year crown along with his side Bayern Munich winning the treble, it remains unlikely that anyone other than Ronaldo or Messi can win the 2013 Ballon d'Or.

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Similar to Ribery, in 2009/10, Wesley Sneijder was the chief playmaker inInternazionale's historic treble-winning season. The Dutchman capped a memorable campaign with a World Cup final appearance but Messi still finished top of the world. 
Regardless whether Ronaldo or Messi win the Ballon d'Or, fans the world over have been captivated by their spell-binding performances in recent years. Quite simply the two bring the best out of each other—with Ronaldo, the unstoppable force, consistently clashing with an immovable object in Messi.
Rather than begrudge the winner, the competitors should be cherished as their superb achievements go down in the immortal book of sporting rivalries.
They deserve a slot alongside the likes of Rafael Nadal versus Roger Federer and Ayrton Senna versus Alain Prost.