PSG led in the first leg at the Santiago Bernabeu through Adrien Rabiot's goal, but Ronaldo struck a brace before Marcelo wrapped up a 3-1 first leg victory for Madrid to give Zinedine Zidane's men a two-goal lead to take to the French capital.
Ronaldo has returned to form in spectacular fashion in 2018, scoring 12 goals in his last seven appearances in all competitions, and Villas-Boas believes the Portugal superstar is returning to his best form.
"For his age , what he has achieved and what he continues to achieve, it's amazing," Villas-Boas added.
"I think not only this moment but also Real Madrid have changed recently, particularly after that first leg against Paris Saint-Germain, they're really picking up results and they look solid and strong now.
"As a consequence, Ronaldo is a bit more confident and looking forward to the second leg. I think he can become influential again. In the big moments he is there, he is there for the team and I expect him to be back at this level, for sure."
Neymar is an injury doubt for the March 6 return match after the Brazilian sustained an injury to his right ankle during a Ligue 1 win over PSG's rivals Marseille on Sunday, although coach Unai Emery is optimistic the world's most expensive player will be passed fit.
Cristiano Ronaldo had the chance to score his 50th career hat-trick and 300th Liga goal... but he let Karim Benzema take the penalty to complete Real Madrid's 4-0 win against Alavés.
Classy #UCL pic.twitter.com/GyhtXpsfq7 — UEFA Champions League (@ChampionsLeague) February 24, 2018
"The difficult thing is to live with the strength of Real Madrid in the counter-attack, which is where they can create a lot of damage," Villas-Boas told Omnisport.
"Paris Saint-Germain will try to look for goals, on the counter is the strongest part of Real Madrid so it's really a tricky one. If it was only a one-goal advantage it would be a bit easier but with two goals it can be quite tricky.
"The pressure that Real Madrid would have to withstand if Paris Saint-Germain score can be quite high. Let's see what happens but Real Madrid look very, very strong on the counter-attack so they can create damage as well."
Villas-Boas was speaking as part of the Laureus Sport for Good project that aims to combat social challenges facing children and young people.
"They have more than 100 projects running around the world. For sportsmen it's important to give them a hand so I've been an ambassador since 2011, with great honour," Villas-Boas said.
"I can't praise enough the work they do in social projects, particularly because they are through sports. With sports you learn courage, responsibility, you become healthy and for kids involved in crime, gang violence and social exclusion, it's important to bring them in and teach them values.
"I value a lot the work that they do, hopefully with my contribution we can take their name higher and with the media exposure, we need a lot of you guys so their name can go higher and higher.
"Yeah, just having fun with the kids. The kids were shivering, you don't expect snow here. It was great fun, spent a little bit of time with them, get to know them and promote a little bit Play International as the new collaboration with Laureus."