Minecraft, having been developed for over 15 years, has seen many changes, both small and large. And while the "best" version may differ from person to person, many will agree that there are 3 major periods in Minecraft's history. First, there's the Alpha/Release period, which mainly encompasses when the alpha first released in 2009 to around when Microsoft acquired Minecraft in 2014. Then there's the Acquisition era, which is from when Microsoft acquired Minecraft in 2014 to when they started directly implementing things around 2018. And finally, there's the modern period, which is 2018 to current day.
Release
This period is the beginning of Minecraft. World generation was limited, causing worlds to look very similar. There was very little content, whether it be blocks, mobs, or structures, which cause most newer players to get bored of it fairly quickly.Acquisition
This is the period most people active in communities prefer, as it's at a point where the game has enough content and is stable enough for players to enjoy. World generation is mostly the same, but worlds could be larger and there were numerous structures to explore.
Modernization and Monetization
This period is largely considered the worst. It's when Microsoft started adding in monetization to bedrock edition and updates started to become more compact. It's also around the time the Mob Votes began, which caused a lot of tension and discourse to the community. While there are plenty of changes that are enjoyed community, irreparable damage has been caused.