Halo is one of the biggest gaming franchises ever. It's up there with Mario and Grand Theft Auto.
Halo while big, is nowhere near the same level as GTA or Mario. I will be shocked if Halo 5 sells as much as 4.
How about trying to sell some games and consoles?
You must not understand marketing then. Cashing in on nostalgia is marketing 101 to sell a product.