I was just thinking of this subject and thought of the amazing slice of video game history that the 1990s alone covers.

Going from December 1991 to November 2001, there's a period of a decade where everything from the Atari 2600 to the original Xbox were available new. I looked at the decades as a whole and saw how much range that 1/1/1990 - 12/31/1999 (the calendar 1990s) covered, but saw that if I slid it a little later I could still get the 2600 in but get the entire 128-bit generation in. It's not even really cheat-y as the Intellivision barely missed out on this period, having been discontinued in 1990.
I'm confident there isn't another 10-year period where such a wide range of history was available new. Literally, we are talking about the first successful cartridge-based system to the system that popularized online gaming and internal hard drives, two of the keystones of most modern consoles. We're talking about something that was a contemporary of the RCA Studio II and had 128 bytes of RAM and 2 kilobyte cartridges to stuff that had the early features of the "converged devices" we have today.

The best way to show how big of a range the '90s offered in the way of new stuff is to compare it to the other four decades in video game history:

The '70s had everything from PONG machines to Intellivision on sale new.
The '80s obviously beats the '70s on range, there were still new PONG machines on sale in the '80s (Bentley Compu-Vision anyone?) all the way to Sega Genesis and Turbo-Grafx 16.
The '00s had everything from PS1/N64 to Xbox 360/PS3 new, not nearly as monumental a jump there as the '90s or even '80s but still a big jump.
The '10s had everything from the PS2 to the Xbone/PS4/Switch new, we're reaching the law of diminishing returns here.