those were the days

Those were the days! ({Cliché} Life was better in the past. The days we have been referring to were the greatest of times.) — Вот это была жизнь! Были же времена!

Something that you say which means life was better at the time in the past that you are talking about

Example 1: Those were the days, my friend, we thought they'd never end. — Да, были дни, сейчас их не вернешь.

Example 2: We had no money but we were young and madly in love. Oh, those were the days! (thefreedictionary.com)

Example 3: Ah, yes. The eighties. Those were the days! (thefreedictionary.com)

Example 4: Those were the days. Back when people knew right from wrong.

Also
the good old days — cтарые добрые времена

Example 1:
People hankering after the good ol' days.

cf. [grass is always greener]
grass is greener on the other side of the fence