For me it's pretty simple and obvious, you just have to look at the project's scope.
1 – Can I see design, visuals, graphics, physics, and enemy AI that actually match what this generation is capable of?
2 – Can I feel gameplay that clearly had a team spending a lot of time planning and refining it?
3 – Can I see professional, well-thought-out level design?
4 – Is the sound and music treated at a cinematic level?
5 – The story doesn't have to be complex, but is it convincing and consistent with the game's aesthetic?
None of this comes easily unless it's an AAA game, because it requires massive investment in people, time, and money. That's why it's expensive, that's why it has value, and that's the best the industry can deliver. At the end of the day, something like GTA VI is what will have the biggest impact and move the gaming industry the most, not only by inspiring ambition in the present and future, but by cementing in players' minds what a truly premium project looks like.