This year’s cars have been faster than the 2004 cars during qualifying. Vettel’s pole lap in Australia was half a second quicker than Schumacher’s pole in 2004. However, that’s at least partially due to slick tires and low fuel qualifying nowadays. Also, Melbourne isn’t really a power circuit.
At Monza, the power disadvantage of today’s engines really shows. Alonso’s low fuel pole this year was almost 2 seconds slower than Barrichello’s pole in 2004 and the fastest lap was almost 3 seconds slower.
Zsolt Baumgartener’s back of the grid time at Interlagos 2004 would have put him on pole position in 2003, 18 months earlier, James Allen mentioned in the commentary citing the crazy development pace of F1 at the time, though I can’t recall if the qualifying sessions were affected by rain.
To answer all of our questions, there needs to be an F1 historical series, kind of like Le Mans Classic races. Instead of the occasional demonstration, we could see wondrous things such as this race between Fangio and Brabham.