The one sure way for a player to have a lasting impact on the imagination of the game's global audience is by delivering unforgettable performances when competing for the supreme prizes in the most demanding of circumstances.
Mention of Pele, Diego Maradona, Johan Cruyff or Zidane doesn't conjure up images from league matches. George Best's chances of showing the world how marvellous he was were hampered by the limitations of the Northern Ireland team but at 19 he was so spectacularly devastating in United's annihilation of Benfica in Lisbon that a legend was born.
So amazing, that I know of such greatness even though I was many years yet to be born, but I have seen the tapes and marvelled at such performances on the greatest of stages. Best's legend was permanently embellished when, one week after his 22nd birthday, he supplied that brilliant individual thrust that killed off the same Portuguese club's resistance in the European Cup Final at Wembley in 1968.
For Ronaldo, who turned 23 in February, the most memorable displays in a United shirt have so far come in the narrower contexts. He has had good European nights, and their number has obviously increased encouragingly this season, but there has remained a tendency to let slip opportunities to offer a resonant declaration of just how special his gifts are.
A recent example was the second leg of the Champions League semi final against Barcelona at Old Trafford, which imposed a comparison with Lionel Messi. Ronaldo's industry and commitment were impeccable but as an attacking force much like the first leg he was marginalised, whereas every time the hunched figure of Messi was on the ball, manipulating it with magical close-quarters subtlety and shielding it cunningly even when travelling at deadly pace, those people craving a United victory were desperately grateful for the shortcomings of his teammates.
The debate about the best player on the planet was enlivened that night.
Only fools would expect one man to decide this Champions League final but the greats of the past have done such a thing in these very same arenas (the outcome may hinge on United's capacity to cope with the smothering energy of Chelsea and especially fierce physical drive of their midfield) but Cristiano Ronaldo owes it to his talent to have a big say in the proceedings on the biggest stage in European football has to offer.