I've had this discussions too many time. It's the most dominant car of post-MS era in my opinion. Another thing to mention is that MP4-20 had huge problems with tyres in first 5 races of the season, so it wasn't even second fastest at start of season. Plus, MP4-20 had some of most legendary unreliability issues I've ever seen in F1 and could by no means be called anywhere near best.
That's an overstatement. Which car was better is more than debatable. I think everyone agrees that the combo Alonso/R25 resulted better than the Raikkonen/MP4-20 one but what were the drivers or cars roles on that is objectively unassessable. I recall that F1 Racing magazine chose the MP4-20 as the best car of the year. Oddly enough, Kimi was also chosen as best driver of the season and both choices at the same time resulted quite contradictory with the real WDC outcome.
I also think that somewhat Alonso won that WDC in the first three races in which he had already built a gap from Kimi of 19 points. Along the season, that points gap fluctuated up and down in around 10 points but at the end it was quite similar; in the final WDC standings Alonso got 21 points more than Raikkonen (133-112). So all that, from that point on, Alonso/Renault could afford a conservative approach —more reliability at the expense of speed according to the very Renault's statement— whereas McLaren was forced to a riskier one in order to be able of putting their both cars in front of Alonso's to reduce that big WDC points gap.
The crucial factor ended up being that in general Alonso was able to put his car in between Kimi's and his team mate's, Montoya, and kept putting pressure to bear when the McLaren was clearly faster. The R25 didn't seem so capable in Fisichella's hands, often beaten by Button's BAR-Honda, MS's Ferrari and some Toyota or Williams . Let's don't forget that McLaren was able to surpass Renault at the WCC just two races before the end of the season and they didn't win it eventually mainly because Montoya DNFed, by accidents, in both last races whereas Fisichella got 13 very valuable points for Renault; the final WCC standings was: Renault 191 - McLaren 182, with 8 and 10 wins respectively. Very close figures in general as not to call it at least near best, aren't they?
At the end of the day, it all depends on the personal perception you have of the drivers' performance. Some could think that the combo Raikkonen-Montoya was better than Alonso-Fisichella and that was what flattered the McLaren. Others could think, especially grounded on what following years showed, that Alonso was in operative terms as fast as Kimi but considerably more focussed, ambitious, race-crafty and adaptable to more different situations, so capable of yielding more points, and it's precisely this what paid off that year.
Edited by juandiego, 26 October 2010 - 13:13.