Halo 4 demonstrates that Master Chief isn't just a Spartan. He's a Spartan-II, and he is at a way higher level than the Spartan 4s. I think the ending cinematic showcases that when the new Spartans lose their composure when they see the Chief walk in. Rather if it's because they thought he died, or because he's the Chief.

Spartan-IIs are legends, and there aren't many left. I feel very empowered and mythical when I am in the shoes of Chief. Even after playing as other Spartans in Reach. You can tell that he started off being a badass since he was abducted.

I think as long as they keep demonstrating how much on another level Spartan-IIs are, I feel like he's always relevant.