As someone who only had preboxed adventures started in 3e:
Non-Starters:
3e: Red Hand of Doom - had a great blend and fun challenges, and had a real threat. A lot of my campaigns
4e: King of Trollhaunt Warrens - had a really fun, psudo-faerie feeling to it that I enjoyed. I liked the use of a cunning troll as a major threat. The sandbox books (Threats to the Nentir Vale and Vor Rukoth) get an honorable mention because they are weren't adventures but they did inspire them.
5e: Wild Beyond Witchlight - because it really is nice to dig in to the faerie stuff, and even if some parts of it are silly, it still adds a lot of lore and things, and it has some interesting situations that come up.
Starter Adventures:
3e: The Sunless Citadel - a great intro dungeon delve that established some great tone.
4e: Reavers of Harkenwold - Good tone, interesting action, a cool threat for the players to oppose.
5e: Dragons of Stormwreck Isle - it's an introductory adventure with a small sandbox, a clear scope, plenty of dungeons AND plenty of dragons, that lets the characters solve their problems in a variety of ways. Phandelver might be a better adventure, but Stormwreck is a better starter, I think.