The best events I remember have been the Valentione's event, where we entered a duty with 1 other player. There is something altogether different about doing a duty with only 1 other person. It's just more personal and feels like it's proof of a missed opportunity when you actually do it.
Another good event was the Halloween event which has involved games in a haunted house that can actually be failed, and make the players work together to overcome the traps. It was actually somewhat challenging - literally more challenging than any actual dungeon lol. There's nothing quite like this in the game, especially when it comes to casual content, yet right there they proved they are capable of it and doing it well. It was fun, too.
There was a good easter event that involved finding eggs and getting an egg mount. I liked that because it's simple yet it's what easter is about.
The jump puzzles for the Moonfire Faire are probably the most consistently good thing but not personally my favorite thing. It also just seemed to repeat lately.
The times they did the choir thing was good. I think that predated bard instruments? It was a bit of a preview.
But mostly, the events are usually just tedious. I like that they are there, I like the stories, but for whatever reason, I just find them a bit of a chore and put them off in many cases. But you've got to have them in an MMORPG because it provides an additional way to shake things up from the norm occasionally, and celebrate an event you're probably not going to in real life (ie. middle-aged gamers probably aren't going out trick-or-treating like they are still kids).
But the examples I gave are more exciting than just this quick story quest and then 10 different letters or interactions with "mystery" people aka all the grand company leaders, retired scions and significant people you met on your journey, who you find out how they are doing.