Invasion is my favorite block hands down, but I feel like the Urza's block was the high water mark for the golden age of MtG
I've played since Fallen Empires and a friend even gifted me a box of Ice Age back in the day. I would dip in and out of the game over those years but Invasion block was a time when I was all in. That was when we got introduced to the shards and I fell in love with Mardu, which at that time was known as Dega. Hell, I even mained a domain deck, such fun times!
Urza's Saga was a time when I was out of the game for a bit. I've always been aware of the cards in that block but in hindsight, what the hell were they smoking when they designed that? Even the art in that block is on point, just a solid block overall.
Universes Beyond almost completely ruined mtg for me. I was starting to look into alternatives like Sorcey Contested Realm but then I found Premodern. Premodern restored my faith in the game.