Capcom's famous Street Fighter II has been through a number of upgrades and spawned several sequels and spin-offs, and while the original arcade release has long been eclipsed by revisions containing words in the title like "Turbo" and "Super", the story behind that first iteration is exceptionally interesting.  Shmuplations has a translated interview with director/designer Akira Nishitani from 1991 in which he lays out all kinds of information about ambitious material that the team had created, but was forced to cut from the final release.  Here's a little of that, and I encourage you to read the entire interview to see it all:

There we were, one month to go before the final deadline. When you’ve come this far, time limits what you can do. With a calm and collected judgment (actually, it was really all my own selfishness) I had to decide what would be cut due to time constraints. Here is a list of some of the plans we had that got abandoned (man, I really wanted to do these!)

• Add weak points depending on whether you hit someone in the head, body, or leg. If you hit someone there, they’d take more damage.
• Add other special weak points outside of those listed above (you can see remnants of those in Blanka’s Rolling Attack, or Vega's Flying Barcelona)
• The computer would change its tactics depending on who it was fighting against (it does do this a little bit, but we wanted to do something more detailed, like the AI knowing how close to stand to each individual opponent, etc)
• Players would take more damage than normal when dizzied.

There's also mention of the original backstory for the game (though it doesn't compare to what the actual saga actually became), and what's especially amusing is that a typo crept into the game's subtitle and nobody noticed it until the very end of development.  If Nishitani hadn't been able to work some last minute graphic layering magic, we'd all have been playing Street Fighter II: The World Warrier [sic].  While I like the later Street Fighter sequels, there's something about that original arcade release that feels most pure before all of the high-level combos, complicated super moves, and other such things that make the game popular with pros were added.  I can do a Hadouken into a Shoryuken without fail, but some of the extended moves from Street Fighter V are way beyond me.