An estimated 1 billion TV viewers watched India play Pakistan in the Semi Final of the Cricket World Cup

"It’s estimated that a television audience of more than a billion people watched India play Pakistan in the semi-final of the world cup of cricket. To put that in perspective, around 0.7 billion people tuned in for the final of the last football world cup in South Africa.
At stake, in sporting terms, was the chance to contest the world cup final against regional neighbours Sri Lanka. India won as it happens, by 29 runs for those who understand cricket. But even for those who don’t have the slightest idea what the sport is, the match is still of great significance.
This is the first time either country has hosted the other in a cricket match since the Mumbai attacks perpetrated by Pakistani-based militants. Relations between India and Pakistan, tense at the best of times, have been at a new low ever since."

Source:  EuroNews, 30th March 2011
Note - No source quoted for where the estimates actually come from