Pelé has to be there, his selection is non-negotiable, IMO.
One of the spots goes to Beckenbauer for me, these lists are often stacked too heavily in favor of forwards.
- Had a prodigious start to his career, reaching the 1966 World Cup final before he turned 21 and finishing as the joint 3rd scorer — the fact that a youngster like him and peak Charlton (who was a titan of European football at the time) cancelled each other out in midfield speaks volumes.
- Remarkable consistency: world class from the mid '60s to the mid '70s, earning Ballon D'Or nominations throughout the period, etc.
- To add to the previous point, he was brilliant in every World Cup participation...1966 obviously, 1970 where he played on vs. Italy in the semis despite dislocating his shoulder, and 1974 where he helped bring the overconfident Dutch juggernaut of Cruyff and Michels to its knees. Also elected to the European Championship team of the tournament in both finals participations.
- Exceptional leader: one of the best in the history of the game, a trait that is lacking in someone like Messi (this isn't to target and denigrate him, just the first name that came to mind).
- Redefined how defenders play in a lot of ways — almost peerless in that respect because he will always be THE Libero, irrespective of who played (or will play) since his retirement.
- Helped establish Bayern Munich as a genuine force on the European stage. They were relative minnows before his emergence, all things considered: German champions only once (whereas Nürnberg, Schalke, Kaiserslautern, Berliner FC, Dortmund had won multiple championships before the Bundesliga consolidation) and hadn't made any inroads in major continental competitions. His impact was felt as early as 1967 when they won the European Cup Winners' Cup vs. Rangers. Not many cemented an elite club (that is still elite) in the way he did, apart from probably Di Stéfano with Madrid and a couple others.
- Winner in every format: World Cup in '74, European Championship in '72 when he put on one of great shows in tournament history with Netzer, 3 straight European Cups from '74 to '76, 4 Bundesliga titles, etc. Again, something not every GOAT can match.
- Pleasing to watch and a purist's dream, which counts for something surely. Also, he is the greatest reader of space and organizer in the defensive third, IMO — maybe not the greatest tackler or the most physical, but unmatched in the way he interpreted and reacted to things — like how Cruyff saw space in the final third.
- Distinguished older player — in a juxtaposition with the first bullet point. Won his second Ballon D'Or at age 31.
There are almost no flaws in his resumé when you consider his overall skill set, breathtaking consistency and accomplishments at an individual or collective level, the only thing(s) holding him back from being universally acknowledged as Top 3 player is that Bayern didn't totally dominate Bundesliga against Vogts/Heynckes/Netzer's Mönchengladbach and his position isn't valued as much, even though he was a difference-maker of the highest caliber and stood a tier above contemporaries with a similar function.
Can't choose between Maradona and Messi for the last spot, coin-flip decision because they are both fully deserving.