How many years has it been since release of first my little pony?

Following the original My Pretty Pony toy that was introduced in 1981, My Little Pony was launched in 1982 and the line became popular during the 1980s.

The current incarnation of My Little Pony, unofficially known as the "Generation Four", was launched in 2010. It is set in a fictional location named Equestria, and the main characters include Twilight Sparkle, Spike, Rainbow Dash, Pinkie Pie, Applejack, Rarity and Fluttershy. Television series My Little Pony: Friendship Is Magic, theatrical film My Little Pony: The Movie, as well as other related media accompany the current line-up. This era generated a fandom among grown-ups with the success of the television series.

My Little Pony: Equestria Girls, the anthropomorphic spin-off, was launched in 2013.

My Little Pony: Pony Life, a spin-off reboot series, is set to launch in 2020 featuring a new, chibi animation style.

My Little Pony: Pony Life premiered early worldwide on Treehouse TV in Canada on June 21, 2020.

i think its the outcome of people's preferences.