Does it even need to be compared to consider itself successful?
I would argue that the fact it performed well for the company using their own metrics is enough to warrant it being a success. I don't think it needs to be compared to other cable networks OR streaming platforms, considering Prime Video was not ever meant to be in direct competition to Netflix of Disney Plus anyways. It was always designed to promote Prime subscriptions, which incentivizes people with active subs to continue purchasing goods online.
I think just counting the 9.x billion total minutes it has is more than enough to consider it meeting and surpassing Amazon's own expectations. I personally think the comparison to any other show is mostly arbitrary. If we're talking about the top 15 Originals specifically, this is such a dubious category that doesn't really account for 'success'. For example, would anyone say House of the Dragon (if considered an Original series) was less successful for not making that list? Not really.