He's emblematic of Halo and is actually a character with some depth if you're into the expanded universe. He's the most badass guy in the entire extended fiction bar none and almost absolutely no one could keep up with him.
Noble 6 was great because we knew that the SIIIs were well trained and capable of awesome shit. The notion that the character was a "hyper-lethal vector" that performed black ops for Ackerson was a neat idea, even if the character themselves purposefully lacked depth. They made up for it with Reach's ending, which was awesome. ODST has Buck, who continues to be Nathan Fillion, which is always acceptable.
The introduction of Locke as an alternative to Chief is somewhat problematic because the original narrative of his reveal is oppositional which directly generates an analogous opposition between 343's new lore (which hasn't exactly been well received, though certainly not absolutely panned) versus Bungie's old lore, which was more classic sci-fi. Outright replacing Chief with Locke evokes a sort of "OUR MASTER CHIEF IS SO MUCH BETTER THAN THIS OTHER DUMB MASTER CHIEF" feeling. Instead of Locke merely being a character that the players could have some interest in, his character is actively built in opposition to that of the Chief's. It's made even worse with the fact that Nightfall was poorly written and, instead of establishing Locke as an interesting character that's capable of feats of badassery that could rival the Master Chief, established him as an incompetent leader that lost almost his entire team on what should have been a simple mission.
For what it's worth the Gamestop trailer actually did a way better job of making Locke a badass. He looked like he was in fucking Vanquish or something.
I mean, really this analysis could go towards any of 343i's newer characters. Sarah Palmer? Kind of an asshole, actually antagonistic, somewhat incompetent. She didn't get fleshed out until she got her own spinoffs and comics, and at that point everyone was mortified that they were going to try and replace the Chief with her. Thorne and the rest of Majestic weren't even real people. You could give them any other faces, names, armor, and series of character traits and they would be wholly indistinguishable from what we got. The SIVs, the new generation that's supposedly much more advanced than the SIIIs and SIIs with their new armor compensating for their relatively weaker augmentations gave birth to a generation of dude-bro super soldiers that lack discipline and character as a whole.
It's probably harder to capture that SII and SIII lightning in a bottle again, though. SIIs are a group of super soliders raised since childhood to be the most advanced combat unit in the history of humanity. The books provide ample examples to show their cunning, discipline, and character depth through their interactions within their tiny family. The SIIIs do as well, but to a slightly lesser extent. The SIVs unfortunately have no such story. Helljumper, maybe, but it's mostly about Buck, who was already pretty much one of the best soldiers in the UNSC.