The era: Early '90s
The games: Street Fighter II, Mortal Kombat, Fatal Fury 2, World Heroes
The babes: Chun-Li, Cammy, Sonya Blade, Mai Shiranui, Janne D'Arc
Stage in evolution: Instead of rescuing powerless damsels from whatever monster that happened to pass through town, most gamers spent their time playing as girls in countless fighting games. Thanks to Street Fighter II (specifically the leggy Chun-Li), every brawler out there had to have a sexy combatress in its ranks, with each new franchise trying to "out-sex" the other. Chun-Li was slutted out of town by Cammy, but none could hold a candle to Mai, who may very well be the first case of bouncy animated boobs. Gaming magazines were abuzz with commentary on what Mai's bobbing bosom meant for the industry - it was like witnessing (half-naked) women entering the workplace for the first time.
It wasn't all scantily clad scrappers, though. Sonya Blade and Janne D'Arc managed to make a splash despite owning a full set of clothes. In any case, graphics had progressed to the point where male and female sprites were easily distinguishable, and the latter was starting to become hot as hell. The same NES kids who hated girls years earlier were now totally cool with rubbing up next to the opposite sex. This is where video game crushes truly began.
What these games taught us: If a girl hasn't been kidnapped, it's because she's a thick-thighed master of combat who fights with as little clothing as possible. It would just get in the way, after all.