I can't think of any movie that I've seen more times than Holy Grail, but that doesn't make it my favorite. It's more about availability. My favorite movie (Tarantula) was made in 1955, but it wasn't released on VHS until 1997 and not on DVD until 2011 (Blu-Ray 2019). Not sure when Holy Grail came out on VHS/DVD, but I'm sure it was more widely available.Since I saw it so many times it felt like a 30 minute movie towards end, I have to say Monty Python and The Holy Grail
No other movie comes close to number of times I saw it.
its not exactly obscure though.
Aliens, Terminator 2, and the Abyss must all be enjoyed in the extended/directors cut editions.