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You can call death note as the best for its unique plot, aot for its action, one piece for its adventure, and steins gate for its genius plot. But people often judge an anime around those aspects. But when it comes to watching, do we really feel the anime that we're watching? Like FMAB for example, had me tight on my sit only for 60+episodes (mind you that one piece has 1000 episodes yet it only became interesting after episode 100 or so) but FMAB is different, from the moment I started watching it, I was already intrigued and entertained as I unravel the mystery and specticle. accompanied by its action and twists Death note in comparison, yes it had a unique plot as the MC is the villain, yes it was definately interesting, and yes it was definately one of the greatest mind game anime, but it fells short on the second half. AoT, one of ur typical shonen, but with the unique plot revolving around titans where the MC fights them off, but as the series progresses, MC also becomes somewhat a villain. So it's another good anime. And then we have steins gate which is about time travelling, not ur typical time travelling anime as scientific theories about time travelling wereexplored throughout the series. But letting that aside, I dont judge anime base on plot alone, also judge them base on how well it is executed and how flawless the story feels. Other animes failed to capture this, but FMAB managed to and thats why I think its the best.