The Romeo Must Die era to be honest. It's what made her a global star but technically, it's Age Ain't Nothing but a Number, she had more hits. Sadly, it was slept on and Aaliyah, her family and team pretty much wanted to era her affiliation with R. Kelly that's why it's slept on and not celebrated.
One in a Million wasn't exactly a big era for her, it's what prompted her to crossover to film and sing soundtrack songs to breakthrough into the mainstream even more. Sadly, despite being her magnum opus, her Aaliyah album was actually close to flopping before she passed.