I think it has to be Lee. As much as I rate him in his 2008-era attack leader spell, and think he was better than he actually turned out to be (damn the "be a 150km/h bouncer/yorker enforcer because McGrath's both the workhorse and the attack leader" thing), he simply didn't actually do it.
Vaas was an absolute gun on dead tracks (for seamers), and was the only quick of note to ever come out of SL pre-Malinga. Such a smart bowler, and he's criminally underrated. Does not deserve to be in this discussion at all.
Zaheer had his spell of being the best bowler in the world circa-2011. Swung the ball at quick-enough pace, reversed it, was canny enough to get blokes out, made Graeme Smith cry. Not terrible.
Never saw Kapil live, so can't really comment. Maybe he's worse in a pure bowling sense, or maybe I'm Moeen-ing it up with a "he can bat, therefore he can't be as good as a pure bowler" argument. Something something Appeal to Spreadsheet.
Ntini? Hmmm, maybe he was worse than Lee. Reliant on his awkward angle, pace and bounce -- so when things went wrong for Ntini, he could look toothless. But when he was on, that angle-in, seam-away MO was deadly.
Broad may not be an ATG bowler, per se, but he's a bowler of ATG spells. I can't think of another bowler who is so randomly destructive while seemingly doing nothing different to usual. As much as I want to hate the guy and call him ****, he's a serious bowler.
Anderson has bowled with pace and movement in an era that, historically, hasn't been especially kind to the bowler-folk amongst us. When he's hooping the ball around corners he's damn near unplayable; when conditions aren't in his favour he's economical and still incisive. Certainly above Ntini.
I suppose the other argument could be for Mitchell Johnson. Spent probably, what, 200 of those 300 Test wickets being absolute shite and fluking an 8-fer whenever he played in Perth or South Africa? All came together in 2013/14 for the Ashes and the Saffa series that followed. Had an immense ceiling but, a bit like Lee, he didn't actually do it for most of his career.
So I reckon its Lee vs. Ntini vs. Johnson vs. Zaheer (with the only thing making it competitive being my pro-Lee stance). Anderson, Kapil, Broad and Vaas a class above, the rest sitting in various classes above that.
You know what, Lee's a dirty Tory. Screw my pro-Lee 'stymied by his role in the attack' argument. He's objectively the worst to 300.