'99, '03, and '05 were all
dominant playoff runs. You're probably distracted on the box score by Duncan's runs coming in that brief window where NBA ball was the absolute slowest its ever been, and because most of Duncan's defensive contribution doesn't show up on the stat sheet. But in those three years Duncan was absolutely carrying the team all the way through the playoffs on both sides of the ball in a manner that Curry has never done, and overcoming some big-time opponents who should have had the advantage (like the Shaq-Kobe Lakers or the defending champ Pistons) in the process.
'99 in the WCSF he tore apart the Shaq-Kobe Lakers to the tune of 29-11-3 and 2 blocks a game in a series where Sean Elliott was his #2 scorer and some of their wins were in the 70s or 80s. Then he dismantled the Knicks in the Finals with 27-14-2 and 2 blocks/game. In the last two games of that series he put up 28-18-3 and 3 blocks, then a 31-9-2 elimination game that they won just 78-77.
'03 he had the 28-12-5 series in upsetting the defending champ Shaq-Kobe Lakers, then 28-17-6 and 3 blocks a game taking down Dirk's Mavs, then a ridiculous 24-17-5 and FIVE blocks a game in the Finals. In the Game 6 close-out game he put up 21-20-10 with 8 blocks in an 88-77 win, leading all players on the court in all of those categories.
Steph has never had a single playoff run that measures up to the 2-way dominance that Duncan showed in '99 and '03. Not to mention Duncan's numerous other dominant series like 27-17-4 and 2 blocks/game against the '01 mavs, 26-11-6 and 6 blocks/game against the '02 Sonics, 29-17-5 and 3 blocks/game against the '02 Lakers, 32-12-4 and 3 blocks/game against the '06 Mavs (the series that ended with Duncan's 41-15-6 and 3 blocks Game 7 failed to win the series only due to Manu's unfortunate foul), 27-14-1 and 4 blocks/game against the '07 Suns.
If Steph wins two more titles with dominant performances in the process and finally gets his Finals MVPs, then he'll be in Duncan territory. He's not there yet.