I cannot really say much about Generations as they overlap a lot but for me it was the early to mid 90s. SNES and Mega Drive being the stars, when the Playstation popped up. The PC Engine (Turbografx) has some decent games too.
That's all for purely nostalgic reasons mostly, but lots of great series first came out around that time or got their first major graphical updates, making them more main stream.