While most of us continue to be starry-eyed about MGSV: The Phantom Pain [official site], there has been no shortage of Internet Grumbles about its ending, and concerns that it wasn't finished-finished (possibly related to Kojima and Konami's latest round of spats?). I'm not going to get into OPINIONS on that stuff myself, primarily because I'm not personally invested in MGS lore, but yeah, there really was an original, longer ending sequence with MORE RIDICULOUS DRAMA and arguably a greater sense of closure, both for Big Boss/Venom Snake himself and in terms of closing the loop between the two main Metal Gear Solid timelines.
This other finale, set on a jungly island, was partially completed before whatever happened happened, and is included on the MGSV bonus disc from the PS4 collector's edition. You can watch the whole, 18 minute sequence below. Spoilers, inevitably.
N.B. I am well aware that some of you will already be aware of this, and have seen it before. This post is for everyone else.
In the lost episode 51 sequence, we see Big Boss/Venom Snake head to a Lord of the Flies-style island, occupied by a militarised child army lead by Eli, the clone son who will eventually become long-time MGS villain Liquid Snake. Enormous Metal Gears, a big old fight involving Big Boss's entire private army, and equal parts sadness and silliness are involved. It's unfinished, but a surprising amount is present and correct. What do you think, is this a more satisfying ending than the one we got?
The ending isn't the only aspect of MGSV which fell onto the cutting room floor, however - there have been many hints of a third chapter, titled Peace, that didn't appear in the finished game, as well as many early trailer shots that are nowhere to be found in MGSV. The video below from HyperBitHero attempts to summarise all of it, as well as applying extra scrutiny and context to both the finished and cut endings.