Brawl has much less of a storied competitive scene, and thus there's inherently less metagame development. Fox is considered the best character in Melee, but the margin that Meta Knight dominates Brawl by is far, far larger. Nowadays, competitive Brawl is pretty much dead, Melee still has large tournaments.

I think the Melee tier story is far more interesting than the Brawl one since there's far less motivation to develop the lower tiers in Brawl. In Melee there's still some development in lower tiers like Game & Watch and Yoshi that could see them climb the ranks.