I'd say Warning is my favorite album, but anything pre-2004 is solid gold for different reasons. I think the best built album is unquestionably Nimrod, but Insomniac is the most fun. Dookie is just pure childhood nostalgia. The stuff before then is fun, too, but a lot more raw and less fully built.
Here's an anecdote:
My family moved up to Oregon when I was about 7, and there was a music video channel called The Box. It was one of those situations where songs would scroll across the bottom and you could call in to make requests. So my cousins were all big into gangster rap, which is fine, but unlike most of them I was actually from the hood and wasn't impressed by music video drive-by shootings and shit lol. So Gangster's Paradise is playing, and everyone is all into it, and then the next video that comes on is completely different. Not just the music and the energy, but the colors. I was like ".......This... this is amazing... what IS THIS???". It was the video for Basket Case, and my love of Green Day has persisted ever since.