My all-time formation (I'll leave out Maradona who, despite seeing a ton of, most of it was via tape recordings and youtube videos. Wasn't born when he was at his absolute peak).
I'll also try to make the team functional and balanced, as the above formations, great as they are, are too offense oriented, which makes sense considering many of the greats deserve a spot and are offensive players. So as a result, some names will be left out for the purpose of practicality. I'm basically making this as if I were building a real team.
The formation is 4-1-3-2.
Goalkeeper: Gianluigi Buffon.
The best Goalkeeper of the past 20 years bar none, and the best of all time IMO. The reason why I say he's the best of all time is I think goalkeeping has evolved so much in Football. From training methods to work out regimens to roles (case in point, Manuel Neuer, who's basically a libero). I think many limit goalkeeping to shot-stopping but I feel there's a distinction. Obviously you have to be a great shot-stopper, which Buffon undoubtedly is, but making great saves is not everything. In fact, Iker Casillas has probably made more miracles than Buffon and has had better reflexes in his prime, but he doesn't command the area, organize the defense, and absolutely dominate the 6-yard box like Buffon. He also has made way more mistakes, which is a testament to Buffon's technique, fundamentals, and positioning. A true titan, and an absolute footballing legend. Nobody deserves to be in the upcoming Champions League final more than this guy.
Left Back: Javier Zanetti.
What does it say about how good this guy was that I have him as my left back when he's mainly known as a right back? But that's how versatile he was. In his best ever season with Mourinho in 2010 (when Inter won the treble), Zanetti mainly played as a defensive midfielder and a left full back and excelled at both roles, despite playing "out of position" (Maicon was the right back). Ambidextrous, physical, reads the game like no other, NEVER seen him taken on, otherworldly stamina, terrific on both ends of the pitch. A legend.
Center Back: Alessandro Nesta.
The single greatest man-to-man marker I have ever seen. The greatest tackler I have ever seen. The best anticipation I have ever seen. Commanding in the air, physically imposing, quick, agile, flexible, fundamentally perfect. An absolute rock. AC Milan wouldn't have been the dominant force in 2003-2007 without him.
Center Back: Fabio Cannavaro.
Nesta may have been the best defender I've ever seen on a consistent basis, but I don't think he (or anyone else) has ever reached the highs Cannavaro did in the 2006 World Cup. The single greatest defensive display I've ever had the pleasure of watching. Italy conceded two goals all tournament: One was an own goal in the group stage, and one was a dubious penalty scored by Zidane in the world cup final. Says everything, really.
Right Back: Cafu.
Imagine this: There was a time when AC Milan's defense consisted of Cafu, Stam, Nesta and Maldini. How's that for scary? Cafu redefined his position. Yes, Brazil always produced terrific attacking full backs but unlike the likes of Roberto Carlos, Cafu actually knew how to defend too, having been a staple in Serie A with both Roma and Milan. With two world cups to his resume and another world cup final appearance, as well as two champions league trophees and two Serie A titles, they don't get much more accomplished than this guy.
Defensive Midfielder: Patrick Vieira
To be honest, good as he was, he might feel out of place compared to other guys on this list, but in his position, few were better. It just happens to be an unheralded position. It's also a relatively "recent" position, made famous by Dunga. But in his prime, Vieira was something special. Captained Arsenal to a legendary invincible EPL run, and won the world cup with France. A workhorse in midfield with underrated technique to boot.
Central Midfielder: Xavi.
Perfection. In his prime, he never set a foot wrong. Nobody had that sort of combination of vision, calm and technique. Few players free up space with a single touch like he did, and he was at the heart of arguably the greatest side in history as Barcelona terrorized Europe in the Guardiola era. Truly helped define an era of football and there wouldn't be a tiki-taka (much as I hate that term) without Xavi. Oh, and I heard the Spanish national team wasn't too bad either, and he had a thing or two to do with it.
Central midfielder: Andres Iniesta.
The most talented midfielder of this generation and the best footballer to ever come out of Spain IMO. Xavi's class is undeniable, but Barcelona and more importantly, the Spanish national team wouldn't have achieved what it did without Iniesta. He almost had all of Xavi's qualities, except he was quicker, had better technique, better dribbling, more offensively creative, etc... He really gave Spain a different dimension in the final third. Other than Lionel Messi, I've never seen a player operate in tight spaces as well as Iniesta. Legend has it that he and Xavi have given away possession a total of 3 times in their 4 seasons under Guardiola (I just made that up but it wouldn't shock me, lol).
Central midfielder: Zinedine Zidane.
Elegance, genius, efficiency, and the first touch of a god. The greatest playmaker of all time. Nuff said. Truly a once in a lifetime talent.
Forward (false 9): Lionel Messi.
I mean, it's Lionel Messi. I really don't need to add anything else.
Striker: Ronaldo (Brazil).
The greatest striker of all time. At his best, simply unstoppable.
Squad shape:
------------Buffon------------
Cafu--Nesta--Cannavaro--Zanetti
------------Vieira-----------
----Zidane--Xavi---Iniesta---
-------Messi--------------
-------------Ronaldo----------
Substitutes:
GK: Iker Casillas
D: Paulo Maldini (I don't feel good about leaving him off, so he could easily replace Zanetti)
D: Lillian Thuram
M: Andrea Pirlo
F: Ronaldinho
F: Cristiano Ronaldo
S: Thierry Henry