And why is Button a weak WDC? because he didn't dominate like Michael did in the past?
Seriously, this whole thing about "weaker or stronger WDC" is just nothing more than pathetic semantics. A driver is here to win the WDC, whether he wins it by one win or 18 wins, that doesn't matter. He still a deserving WDC, and by default was the best driver that year. Everything else is just opinions...
You just don't seem to get it. Here I will write it as simply as possible.
2005 - Alonso beats Kimi to the WDC. Kimi was already considered one of the best in F1 at that time and many were only waiting when he will win his first WDC. Alonso also smashed Fisi his team mate by 75 points.
2006 - Alonso beats Michael to the WDC. Michael is easily one of the best drivers ever in F1. Alonso again smashes Fisi by 62 points.
2007 - Kimi beats Alonso & Hamilton & Massa. Kimi beats a two times champion and also beats Hamilton who many considered a world champion in waiting. Kimi also beat Massa by 16 points.
2008 - Hamilton beats Massa & Kimi to the WDC. Hamilton beats a world champion and Massa to the tittle.
2009 - Button beats Rubens & Vettel to the WDC. Rubens is considered by many to be an average number 2 driver which he was his whole career. Vettel is considered by many to be very good but he had a bad season with driver mistakes and car unreability. Button beat Rubens by 18 points.
See where this is going? All the current WDC's had a much harder time racing against much better drivers than Rubens or Vettel. Alonso beat Kimi and Michael, Kimi beat Alonso, Hamilton, Massa and Hamilton beat Massa & Kimi to the tittle.
There's a big difference between Rubens, Vettel and the rest of drivers I have mentioned. What I am trying to say Button had an easy competition compared to what Alonso, Kimi and Hamilton had when they won their WDC's.
There's a big difference beating an average number 2 driver like Rubens or beating a 7 time world champion don't you think?