For the statistically inclined, check this post in cricinfo: 15000 and counting. Some excerpts and my take:
When Sachin Tendulkar reached his fifty in the second ODI against South Africa, he went past another milestone in a career chequered with record-breaking moments. Tendulkar became the first batsman to accumulate 15,000 runs in ODIs - he was the first to 10,000 runs as well. In the 189 ODI innings he has played when India has won, Tendulkar has scored 9061 runs at an average of 56.98, with a strike-rate of 89.72, all figures higher than his overall average. Which means his contribution has been vital for India wins. Conversely, India wins if SRT performs well.
He averages 47.96 in 36 finals (of tournaments involving three teams or more). Which means the weak argument that some critics present that he is not a big match player is horse shit. He averages 89.10 at a strike-rate of nearly 100 when the team has won in a final. Which could mean, the only time that we have probably won a tournament final is thanks to SRT.