Roughly 20y DeepBlue to AlphaZero. I don't think that is comparable though. Use of deep neural networks was what made the machines starting with AlphaZero dominant again. I.e. we're already in the new paradigm.
> In comparision, Nakamura had the assistance of an older version of Rybka (about 200 points less than Stockfish's 3200+ rating), and it ran on a 2008 MacBook. Of course, he also had his 20-plus years of chess knowledge in play.