Killzone deserves a spot on this list primarily because with each passing day, it turns into more and more of a museum piece. You really need to take the time to seek out what Sony were once-calling the 'Halo killer', especially when what it morphed into was a far more realistic military shooter with a very drab aesthetic. You can see what they were going for (and remember, this was before Modern Warfare revolutionised military shooters), and although Killzone developed something of its own fanbase precisely because it was so aesthetically different to the technicolour world of Halo, it never managed to reach similar heights.
