The early 90's were a really awful time for snooker.
Davis was largely spent, White and Parrott were good but not greats and the class of 92, Ebdon and Doherty were all still well before their peak.
Their opponents in the worlds aren't really comparable of you ask me.
In 2001 he beat Higgins, one of the all time greats in the final. In 2004 he beat the UK champion Maguire in the first round and Hendry in the semi's (ironically probably his easiest run), in 2008 he beat Hendry and Williams on the way to the final, in 2012 he beat Neil Robertson and Mark Williams, in 2013 he beat Trump and Bingham and this year he beat Williams, Ding and Selby.
He's had relatively easy finals across the 6 but he's has utterly brutal runs to those finals. In the 1990 win Hendry only faced Parrott who was a player of any note, in 1992 he literally didn't play a seeded opponent until playing against a 107 year old Terry Griffiths in the semis. In 1996 he managed to win by playing against Jason Ferguson (yes that one), Gary Wilkinson, Darren Morgan, Nigel Bond and Peter Ebdon. Yes, that's right, he won the World Championships by playing 5 players that had a combined 2 ranking tournament wins in their careers up to that point.
It wasn't until 97-98 that the level really started to heat up. Hendry was clearly much further above White, Parrott, Bond and McManus than O'Sullivan is above Higgins, Williams, Selby, Robertson, Trump, Ding etc. but that's because the latter group are vastly superior players by and large.
Ronnie hasn't been able to dominate an era because at any one point because pretty much since he arrived on the scene he's had peak Hendry then peak Williams, peak Higgins, peak Robertson, peak Selby and now peak Trump to battle with, not to mention players like Murphy and Ding who are at least on a level with Parrott and White and Hunter who would have been if his career hasn't been cut short.
The arguments that Ronnie isn't the greatest have been pretty ridiculous since he took a year off then came back and won at a canter in 2013 really. This win just put the nail in the coffin.
Hes also won a triple crown event in each of the last 9 seasons, equalling Hendry's best streak which is pretty mental when you think he's currently 44.