Okay, so let's talk about Sailor Moon and how she overhauled the Magical Girl genre.
Actually I think some Westerners give Ms. Moon a tad bit too much credit — hers is usually the earliest MG show they're familiar with, so they tend to dismiss everything else as a Sailor Moon "ripoff." Sailor Moon certainly didn't invent the MG genre, nor did it invent most of the tropes it used, since most of those were borrowed from earlier MG shows. No, what made Sailor Moon revolutionary was the way in which it combined all those tropes, the result of which proved so popular that it became the de facto guide on How To Construct A Magical Girl Show.
Sailor Moon is a cross-pollination of the various pre-existing MG genres. From the male-oriented Proto-Magic-Warrior genre, it took the focus on fight scenes, the "save the world" high-stakes plotline, the nude transformation sequence, the "I am so-and-so"/"In the name of the moon" post-transformation speech, the Cutey-Honey-initiated trend of having all the baddies be scary-looking females, and the overall theme of the Magical Girl as a badass superheroine. From the girl-oriented Object-User genre, it took the endless parade of foofy outfits, the sparkles, the PINK, the blinged-out magic items that look suspiciously like plastic merch, the basic origin story of "muggle girl gets cool magic trinket out of the blue," the cutesy otherworldly critter who gives the girl her magic trinket and serves as her mentor, and the overall idealistic outlook and tone.
To this mixture, Sailor Moon added something that was totally new to the Magical Girl genre: the Girl Posse. Up until that point, each Magical Girl heroine was the sole Magical Girl in her universe, with only the muggles for company. Occasionally a MG heroine would have a single MG rival (Meg-chan, Sally 2), but that was about it. But then Sailor Moon took some cues from the sentai genre and gave us not one, not two, but five Magical Girls who fought together as a team, which later grew to
six seven ten thirteen. Ish. Since then, the concept of a team of Magical Girls, each with her own signature color, theme, and combat specialization, all inducted into Magical-Girl-hood via the same systemized ritual, and all bonded together by the power of FRIEEEENDSHIP has become an idea strongly associated with the genre.
Speaking of girl-bonding, the next thing Sailor Moon introduced/enhanced in the genre was lesbian subtext/text. It makes sense: when you have a group of girls who all share intense friendships and who frequently find themselves in life-or-death situations and make heroic sacrifices to save each other and die dramatically in each other's arms etc etc, you're inevitably going have lots of LesYay, whether intentional or not. I can't be totally sure of the gayness level of the older MG series, but from what I've seen, none of them approached the canon-gay of Uranus and Neptune, or Uranus hitting on Usagi, or Seiya hitting on Usagi, or all the subtext between the Inner Scouts, etc etc. At any rate, LesYay is something you often find in Magical Girl shows today — especially blatant examples being Galaxy Fraulein Yuna, Revolutionary Girl Utena, Cardcaptor Sakura, Puni Puni Poemi, Tokyo Mew Mew, Futari wa Precure, Nanoha, Uta Kata, Mai-Hime, Getsumen to Heiki Mina, Heartcatch Precure, and PMMM — and I'm inclined to point to Sailor Moon as the one who started that trend.
Thirdly, Sailor Moon did much to codify the Magical Girl transformation sequence. The details are going to require a whole other post, but in short, Sailor Moon invented/popularized a number of henshin tropes that became popular standards of the genre, and especially popularized the stock footage henshin as a way to save time and money. Prior to Sailor Moon there were a few MGs who used stock footage henshins (Minky Momo, Magical Emi, Sweet Mint) but more often, they'd have newly animated henshins for every occasion — Cutey Honey, Marvelous Melmo, Lunlun, Creamy Mami, and Persia all did this. Post-Sailor Moon, it became standard to have one piece of henshin footage used over and over, to the point where shows that avoid this (Uta Kata) are considered unusual.
And finally, due to the cross-pollination I mentioned above, Sailor Moon was the first Magical Girl show that a) was made for girls and b) had a badass world-saving heroine. Previously, the only superheroines were in the adult-male-aimed shows, and the girl-aimed MG shows tended to be pretty low-key and devoid of violence, for reasons that aren't hard to guess. However thanks to Sailor Moon's influence and success, these days it's the norm for a Magical Girl to be a badass lady.