The Game Was Rigged

Halliday is alive. The are several things in the movie that point to this. For one Ogden should not be around at all yet he is in the game as the curator and he shows up with company lawyers to give away the company. He had to get hired for the cost of a quarter as he was not part of the company (but was). Ogden and Halliday must have patched things up (never mentioned in the movie) and that strongly implies Halliday is alive. As well as being the ones that dropped the portal to the race (in the movie it mentions know one knew who the guy was that found it).

The creators gave away the start of the competition as no one was getting it. The masses needed some help. Halliday invented his own version of a Genesis Device (like in Star Trek) and its in the movie. They put the a-bomb artifact on the market knowing that their rival IOI would buy it. Even Wade says, "they buy everything". Right after that the curator makes a bet w/ Wade with no pre-determined reward on the curator's side (Wade bet "all my coin"). He purposely wagered wrongly on something he for sure knew the answer to. When he did he gave Wade THE MOST VALUABLE ARTIFACT IN THE GAME - the extra life coin. He even kept giving it to Wade even though Wade did not want it.

Ogden and Halliday skewed the game with that. They knew the game killing bomb would get used by their rival and that Wade would be the only one left. Halliday was/is a "builder of worlds" and he accomplished his mission. He deeply wanted to interact with someone that understood him and that was Wade. Both Og & Hal knew Wade had been to the archives looking at their lives countless times. Hal is most certainly a Willy Wonka character and like Willy he is alive. At the end of the movie Wade is taken to the place where it all began: just a latch-key kid playing a video game alone. The old man in the room at the end is not Halliday - the little boy is.