Most of the post is good but you overate some of the drivers, Irvine left Ferrari to join the new Jaguar team but was unable to upstage an inexperienced Pedro de la Rosa, Brundle got similarly hammered by Hakkinen, Patrese got similarly hammered by Mansell, and of course Massa is getting easily beaten by Alonso. His two strongest teammates i would say were Piquet and Barrichello, Barrichello i would say was about 2 to 3 tenths slower than Schumacher, but he then went onto get beaten by Button when it mattered, and an ageing Piquet was probably past his best.
However i cant deny that post Senna Schumacher was the best but maybe the competition wasnt the best.
I'm not sure about the actual figures of HakkinenVS Brundle but eventhough Mika beaten Martin very often, I think the gap was not as big as in SchumacherXBrundle case. Regarding Patrese, yes he was beaten the same by Mansell with the enormous gaps but only in 92 where some people says Nigel had more strengh in the arm to cope with the active suspension car or whatever it was. Anyway, in 91, Patrese beaten Mansell most of the times in qualifying and even got some pole positions. About Massa, it's true that Alonso is proving to be much better as Schumi did. Speaking now about Barrichello, the average gap might be on the 3 tenths region but often in "driver's track" such as Spa, Suzuka, Monaco, Schumacher would be like 1 second faster than Rubens, and this is something nobody else ever managed to do with Rubens, not even Button.
Finally about Piquet, yeah he was old and even mentioned that very explicitely to show some people here, who think age doesn't affect, that we never saw aged drivers demonstrate speed.