Is there a website that has a comprehensive list of all the various editions of the Monopoly board-game there are? I'm sure there's hundreds... but I'm not having much luck finding it online.
It depends on how you define "variations" of the game. At this moment the monopoly wiki has 1144 versions of the game, but it includes fictional editions (Monopoly Capitol City Edition from the Simpsons), predecessors (The Landlord's Game), and so on.
Since you can make-your-own-opoly, there are effectively infinite Monopoly variations.
Well, if you look at my website www.worldofmonopoly.com, you can exclusively see the number held by the world record holder which is 2249 different editions. I also exclusively keep his list up to date and can say that at this point (14th August 2019) he is at 2586 now! The list is continually updated on the website Hope this helps.