clearly you dont know what accessible means, and its clear when someone talking about killzone can only mention graphics and nothing else, that person hasnt played the game.
if killzone is less of a game than halo because it sold less, then XB1 is less of a console than PS4 because it sold less.... oh wait... it actually is. lol.
I know what accessible means, yet somehow people think they can call a game 'less accessible' to explain why it's less popular. Guess what? Making a game accessible' is a point of quality. You have to take time and craft a game that anyone can play and enjoy, without sacrificing extra features that make the game great.
StarCraft was very accessible. Blizzard RTS games always followed the rule of "easy to learn, hard to master". They make their games accessible, and also the best. Quality developers can do that.
And comparing X1 to PS4 at this stage of the game is shortsighted - especially when it costs notably more. At least games are apples to apples - When halo or KZ come out, they cost $60, there's no price disparity to sway people.