If we were drinking in a bar (not that I drink in bars) on trivia night and this question came our team's way, I'd be pretty comfortable (granted, I'd be drunk) guessing Enter The Dragon.
You got to think it'd be a film which was popular at the start of home movies and remains popular enough to day to continue getting releases.
I was able to find proof of 11 releases of Enter The Dragon.
VHS, DVD, Blu-Ray, UMD, CED, LaserVision, Super 8, Betamax, VCD, VHD, and HD-DVD
I wasn't able to find any proof Enter The Dragon was released on China Blue High Definition, but with how heavily Warner Bros backed that format it would make sense if it was. Although they only had the international distribution rights to that film, an I'm not sure if the Hong Kong distributor Golden Harvest hold the rights to that film in Mainland China.
The only film I think could possibly be a contender for this contest is Oliver Twist—depending on which version it is—which according to this list was released on HDVMD. I doubt it, though.
I also doubt anything is pulling through by having been released on VideoNow, the only films having been released on the format—Snoopy Come Home, A Boy Named Charlie Brown, and Agent Cody Banks—not having near enough other releases to come close to the 11 we're currently at with Enter The Dragon.
Thinking on it some of the Star Wars films might tie, but I really think it all comes down to if Enter The Dragon got that CBHD release. 🤔
How do you even research this? I wouldn't know where to begin.
I think your criteria of being released during home movie era and remaining popular makes sense. It also should be a film which appeals to large populations so Enter the Dragon is a good pick and you've convinced me!
I would wonder if there's a Bollywood film that meets the same criteria and could be a strong contender?
I take a guess and then see how many formats for that guess I can find. It helps to know alot of home video formats I can check against.
Tell you though it isn't easy because search engines have noticeably began to suck donkey ass of late. All the skills I've developed have turned worthless as searching no long works the way it did a scant few years ago.
I suppose it's possible Deewaar or Muqaddar Ka Sikandar got a whole bunch of other releases (the second was popular in The Soviet Union) but other than that I don't think laserdisc was ever released in India and that's a whole format. Since some of these films released on near every format every one counts.