Ronaldo's 82nd minute diving header gave Portugal a precious 1-0 lead in Friday's first leg in Lisbon.
But Sweden defender Jonas Olsson says his teammate Ibrahimovic will be key in Tuesday's second leg in Solna in a match which will decide who goes to Brazil next year and who stays home.
Olsson rates Ibrahimovic in the same class not only as Ronaldo but also Lionel Messi. "I've been saying that for quite some time and it's good to see that it's now being recognised," he said.
"I think all three are amazing players with different qualities but what makes Zlatan so incredible is that he combines his technical skills with that physical presence of his, which is very unique.
"He's just amazing. You train with him in the national team and sometimes the things he does are really unbelievable. I've played with some very talented players in England but for me Zlatan is on another level all of his own," said the West Bromich Albion defender.
Ronaldo has won almost every club honour on offer including the Champions League, league titles and domestic Cups in England and Spain although one thing he does have in common with the Swede and Messi is that none of them have won the World Cup.
The 28-year-old was on the losing side for Portugal during the shock Euro 2004 final defeat against Greece, while he provoked controversy at the 2006 World Cup when England striker Wayne Rooney was red carded, before his side were eventually beaten by France in the semi-finals.
Four years later, he managed only one goal as Portugal fell at the hands of eventual champions Spain in the last-16.
Ibrahimovic, top scorer in French Ligue 1 last season, and originally with the option of playing for Bosnia and Herzegovina or Croatia, has only appeared at the 2006 World Cup where Sweden were beaten 2-0 by hosts Germany in the second round.
He came up against Ronaldo in qualifying for the 2010 edition, where Portugal edged Sweden out of second spot with Denmark winning the automatic berth and Portugal booking their ticket via the play-offs.
The two superstars displayed a warm exchange following the Ronaldo-inspired 1-0 win in Lisbon on Friday but admitted the job is only half done.
"It was an important goal and it gave us victory," said Ronaldo. "We could have scored one or two more goals but this advantage gives us confidence for the second leg."
"Nothing is settled yet. It's 50/50. I cannot promise that we will qualify but I will do all I can to achieve it."