Fan dropped on the second day at key centres which basically sealed its fate and the postmortems will happen but the genre of the film always meant an uphill struggle to meet expectations which were mainly there because of a big star like Shahrukh Khan. It could have succeeded but was never going to be a superstar level hit. The highest grossing thriller till date is Holiday - A Soldier Is Never Off Duty at 112 crore nett and that says it all.
The next best are Ek Villain and Race 2 and the list of disappointments in the genre is huge not just over the last few years but since they started being made in Hindi. The last big hit in the genre was Agni Sakshi way back in 1996 and this was mainly driven by Mumbai circuit which had a tax free status.