Having once again launched their quest for success this season on Europe's grandest stage, the game's two biggest stars are close to writing another entry into the history books.
It has long been a case of 'when' and not 'if' the 71 Champions League goal landmark of former Real Madrid and Schalke striker Raul will be surpassed.
Ronaldo has 69 in the Champions League proper; Messi is on 68.
Goalscoring immortality is imminent for one of them. Yet Ronaldo v Messi is a race that will run and run.
Football rarely produces such compelling rivalries between individual players but Messi and Ronaldo's exploits for sworn enemies Barcelona and Real Madrid have cast the duo alongside some of sports' most enduring man-to-man quarrels.
Like Muhammad Ali and Joe Frazier in heavyweight boxing, John McEnroe and Bjorn Borg in tennis and Ayrton Senna and Alain Prost in Formula One, Messi and Ronaldo are destined to be defined by each other's deeds; measured by one another’s excellence.
In this case, though, it is not weight of a punch or the speed of a serve that sets them apart but the regularity of their goals - breathtaking numbers reached at turbo-charged speed.
"I think they need each other," said Michael Laudrup, who enjoyed five years with Barca before joining Real in 1994. "If one scores a hat-trick, the other tries to beat that," he told EFE recently.
It is a theory that Messi has previously refuted, remarking to Time Magazine in 2012: "My mentality is just to achieve more each year. If he [Ronaldo] wasn't there, I'd be doing the same thing."
Nevertheless, in the Champions League in particular, the stats suggest the Barca man is being coy. Either that or a remarkable coincidence has occurred.
Since being matched in close proximity by Ronaldo's move from Manchester United to the Santiago Bernabeu in 2009, both players have hit the goalscoring hyper drive.
The Portuguese has scored 54 goals in 53 Champions League appearances for Real. Messi has netted 51 in 55 matches for Barca in that five-year spell.
Contrast that with the period before Ronaldo arrived in Spain: Messi had 17 goals in 33 European outings for Barcelona - a fine return but little indication of what was to follow - while the Portuguese found the net 15 times in 52 games, excluding qualifiers, for United.
That is not to suggest Ronaldo was anything but a superstar when he signed for Real. On the contrary, he claimed FIFA's World Player of the Year accolade for 2008, having scored in Manchester United's Champions League final triumph over Chelsea.
But the seeds of a blossoming head-to-head tussle were only really sown the following year.
In the 2009 Champions League final, Ronaldo was upstaged by the pocket rocket from Rosario. Messi, who would go on to collect the first of four consecutive Ballon d'Ors, scored the second in a 2-0 triumph as Barcelona passed United into submission.
It proved to be Ronaldo's United swansong, as Real subsequently swooped with a world record €94million fee.
In his first three seasons with Real, Ronaldo scored 33, 53 and 60 club goals in all competitions - numbers that would have been without compare but for Messi's returns of 47, 53 and 73.
Last season, despite injuries, Messi netted 41 goals in 46 games.
That haul would represent a career-defining achievement for almost any other player in the world, but it somehow seemed a slump when Ronaldo notched 51 in 47, reduced the Ballon d'Or deficit to 4-2 and also matched Messi's feat of scoring in a victorious Champions League final for a second time.
Ronaldo's 17 goals in last season's Champions League, a competition record for a single campaign, also surpassed the previous best of 14, set by Messi in 2011-12.
There is more to it than simply fantastical numbers, though. Their respective styles also captivate.
Messi's impish presence, silky touch and dazzling dribbling are in contrast to Ronaldo's dominance through muscularity, speed and precision. While defenders may suffer death by a thousand cuts at Messi's twinkling feet, marking Ronaldo is akin to being repeatedly flattened by a bullet train.
The media image of the two also sees the bold and brash exhibitionist Ronaldo set against a seemingly humble Messi, who still looks faintly surprised by it all.
Had they scaled the summit of European football by the same means, they would arguably not polarise opinion quite as they do.
At 27 and 29, the pair will dominate the football landscape for some time yet and in all likelihood, whoever breaks Raul's record will have only weeks, or even days, to celebrate.
Barring injuries, the new record holder will almost certainly trade the mark with the other - with that exchange set to be repeated over and over, season upon season from here.
In the quest for more trophies, accolades and, of course, goals, Messi and Ronaldo are destined to forever chase one another until they finally hang up their boots - to the benefit of every single football fan on the planet.
