It is very difficult to analyse which is the highest grossing films made ever in Bollywood. It is difficult because we have to take many factors such as inflation, footfalls, nett gross, gross income etc into account. But still few films are made in years which either break records or make new records and become a trend setter for other films to do the catch up.
After lots of research and sources, it is found that all total there are 16 ATBB (All Time Blockbuster) till date. Many might argue with many other films, but it is to be noted that the source I am mentioning are such as Wikipedia, TOI, BOI, and statistics shown by film analysts. Many renowned films are categorized in Blockbuster categories, which itself is a big achievement, since there were times, when in years there was not a single Blockbuster film. Also, many high grossing films are categorized in Blockbuster or Super Hit category, but less grossing films are categorized in ATBB because of the cost value and return of profit value. Generally a film is ATBB if the profits are 3 or more times of the cost of the film (production and marketing included all expense) and also it should cross a standard gross say (approx minimum Rs 100 crore nett gross as on present time).
From studying the collections of each films, we can easily say that Aankhen (1993), was one of the weakest ATBB. Similarly, we can easily say that Sholay (1975), Hum Aapke Hain Kaun (1994) were the strongest ATBB, as there records were much much higher than the films grossed at that time and there records stayed for a long time to be broken. Sholay nett gross record was broken by Hum Aapke Hain Kaun, whereas Hum Aapke Hain Kaun nett gross record was broken by Gadar (2001) small margin. Also, it is to be noted that ticket prices were totally incomparable from Sholay to HAHK time and HAHK to Gadar time.
Many will also argue that 3 Idiots (2009) broke all nett gross records, but it is to be noted that when 3 Idiots arrived, multiplex become a strong factor with sky high ticket rates and also Dabangg (2010) immediately broke many 3 Idiots record within a span of 9 months, which looked really invincible before the arrival of hurricane Dabangg. So, lets wait and watch for few years to check where 3 Idiots and Dabangg stand in the race of highest grossing film ever made in bollywood.
Below is list of ATBB