Pele IMO is a major reason why the World Cup became such a global behemoth, and why the World Cup final became the single biggest sporting match / occasion around. He helped make football a more glamorous sport. I tend to regard, in whatever order, Pele, Ali and Jordan as the sporting big 3, not just because of their success within their sports, but because of their huge significance and influence away from the field, ring, court etc.
I didn't watch him in real-time, but I did watch Maradona in 1982 (including the treatment he received by Claudio Gentile !) and 1986. Because it wasn't possible to watch legends from that era play week in week out in domestic league action, they felt like 'superheroes' when it came to watching them in World Cups. I always laugh when so many people in England bleat on about the hand of god incident in 1986, when English players were hacking Maradona down and elbowing him off the ball throughout the game. Even accounting for the fact that players could get away with much more heavy tackles then, England shouldn't have had 11 men on the field (Terry Fenwick did enough to be red carded at least twice over), by the time the incident occurred. Also it mustn't be forgotten that in the build up to it, his skill to dribble past a couple of England players like they were training cones and pass to Valdano was exquisite.
His achievements at Napoli really cannot be underestimated. Serie A was the best league in the world by a huge distance at the time. Arrigo Sacchi's Milan team only won the league title once given how tough the competition was, genuinely world class players were spending some of the prime years of their career at mid-table Italian clubs, and many of the best Argentinian, Brazil, German and Dutch players were there. Plus in Italian society and Italian football, much of the money and power was in the far wealthier North, so Napoli as Southerners were very much seen as outsiders.