A 2-0 win over Hungary on Tuesday sealed a second successive appearance for Wales at the European Championship, but when Giggs was appointed in January 2018, it was not a universally popular choice.
He came in for heavy criticism over selection and tactics during the summer setbacks in Croatia and Hungary, defeats which left Euro 2020 qualification hopes hanging in the balance.
But a run of eight points from their final four qualifiers sent Wales through to only a third ever major tournament and helped the one-time Red Devils caretaker boss silence his critics.
Giggs' old manager Ferguson, speaking at a fundraiser for international football charity Grassroot Soccer in London, told the PA news agency: "Ryan was always going to be a top man.
"He is intelligent, he has great drive about him and is doing a great job with Wales. And giving young players a chance too. It is fantastic."
Earlier this month, Giggs revealed Ferguson sends him a good luck message before every match and the pair will be reunited again soon.
Grassroot Soccer, who use football as a platform to provide over two million young people in 50 countries with various health services, held a live auction at the fundraising gala in London with one of the prizes the chance to go up against members of the Class of 92.
Ferguson is set to manage the team facing the likes of Giggs plus his old team-mates.
Yet the record-breaking manager warned that his former players still remain as sharp as ever, highlighting the 5-0 win they achieved over Bayern Munich in a 1999 Treble reunion game at Old Trafford in May as proof.
"They are all fit. I'm telling you, they are all fit," Ferguson added. "They played in a charity game against Bayern Munich for the anniversary of 99 and they were amazing.
"Every one of them was fantastic. Whoever wins the prize is going to have to be good."
Glaswegian Ferguson hailed the work of Grassroot Soccer and reminisced about his childhood in Scotland.
The 77-year-old started his playing career as an amateur with Queen's Park before representing the likes of Dunfermline and Rangers.
He would go on to achieve unprecedented success with first Aberdeen and United, who he managed for 26 years.
"Grassroot Soccer is providing a platform and giving kids the ambition to be a footballer because football is one of these great attractions for any kid," Ferguson said.
"You see a ball rolling and a kid will run after it and I grew up in the same vein and being given the opportunity to play football and also for myself to be a professional, that started from a humble background.
"When you are that age you don't think you are going to do it, but given the opportunity you seize it and that is what these kids in Africa will be realising with all the support they are getting from Grassroot Soccer."