The Merthyr and Rhymney AM will stand down before this year's election after 17 years in Cardiff Bay.
Speaking to BBC Radio Wales' Sunday Supplement programme, he said many politicians, including some in his own party, were nervous and sceptical about devolution in 1999.
But that view is now "long gone".
While he was "a very early convert", he said the closeness of the referendum result - 50.3% voted for and 49.7% voted against setting up the assembly - created "a great deal of nervousness".
He said: "My opinion was always the proof of the pudding is in the eating, it's about what the institution does - in terms of social change - that really matters."
Mr Lewis felt strongly that devolution could be used to tackle areas in which Wales was at a particular disadvantage to England, including health, education and combating poverty.
The former chemistry teacher described taking on the education portfolio as "a dream come true" and said reforms to the curriculum and teacher training were two of his proudest achievements.
He said: "The old England and Wales schools-based education agenda no longer exists.
"Wales now has its own distinctive path and own distinctive future in terms of what our schools are going to look like."
He said the reforms happening here were based on "real evidence" and not "ideologically driven", which is what he fears is happening in England with the "marketisation of education".
By implementing a Scandinavian-style model - that includes children learning through play -  he hopes teachers will be better skilled and standards will rise.
"We're not emulating England, we're emulating the best," Mr Lewis said.
This is despite an assumption he believes is made by many that Wales should see England as a "gold standard" and if something different is tried here, it is somehow suspect and second rate.
"I hope, that as devolution has matured over the years, we are finally beginning to break away from that kind of mentality," he added.
"We are quite capable of setting out our own agenda and following it and basing it, in global terms, on what the best looks like.
"That's the real dividend from devolution. That should always be where we're thinking.''

She was cut free from the wreckage by firefighters and was airlifted to hospital. The accident happened at about 10:10.
The emergency services have also been dealing with a collision involving a lorry and a car on the A96 near Inverness.
There were no details at this stage on any casualties.
The lorry ended up in a field during the accident near the Barn Church Road junction.
The incidents follow two separate accidents in the Highlands on Thursday.
A male biker was airlifted to hospital after he was involved in a collision with another vehicle on the A835 north of Ullapool in Wester Ross.
A man was injured in Lochaber after his lorry overturned on A82 near the Corran Ferry terminal.
Wales has "broken away" from England and is now capable of setting its own agenda thanks to devolution, outgoing education minister Huw Lewis has said.
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A woman has died after a one-vehicle crash on the A87 near Broadford on Skye.