Think about it: in Halo 4 and 5, they’re actually exploring the lore a lot more than Bungie ever did. With the 343 games, they talk about things such as the Spartan-II program, something that was never really discussed in Halo 1–3. Also, in the multiplayer, they’re showing off Spartans’ true potential. In, say, Halo 3, you were pretty much a Marine or ODST in a bunch of armor. You couldn’t sprint, you couldn’t quickly clamber up things, and you didn’t have “the most advanced armor ever” (i.e. ground pound and thruster packs). In halo 5, they’re actually showing off more of what Spartans really were in the canon: ultra fast, advanced killing machines.
That’s why I think the campaign in Halo 5 could be the best one yet.