The 46-year-old reeled off breaks of 71 and 126 in the first two frames of the morning session to surpass the record he had shared with Stephen Hendry for reaching the last four in Sheffield.
But despite closing in on Hendry's modern-era record of seven world titles, O'Sullivan is adamant that the Scot's dominance of the sport in the 1990s still makes him the greatest player.
"Stephen is an all-time legend for me, the greatest player," the world number one told the BBC.
"He was the Tiger Woods of snooker. Me, John (Higgins) and Mark (Williams) have all done well, but when he was flying he was a superstar.
"When there's three of us, we're not superstars. But when there's one man dominating the sport like he did, like Tiger Woods, it's a different level."
O'Sullivan had carved out a commanding lead despite never quite hitting top form against Scottish qualifier Maguire on Tuesday, but showed glimpses of his best upon the resumption after a missed black from his opponent sealed his fate.
The Englishman will play John Higgins in the semi-finals after the four-time champion survived a classic encounter against Jack Lisowski.
Higgins showed all his experience to win the final two frames, taking the match 13-12 after falling 12-11 behind.
On the three previous occasions Higgins has beaten O'Sullivan in the World Championship he has gone on to lift the trophy.
Mark Williams booked his place in the semi-finals with a tense 13-11 win over Yan Bingtao, who had hoped to become only the second Chinese player to make the last four.
Williams will play Judd Trump after the 2019 champion recovered from a dismal opening session of the day to reel off eight frames in succession in his 13-8 victory against Stuart Bingham.
"I could not pot a ball and I just tried to dig in and not get too down about it," Trump said.
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