On November 15, 2001, the original Halo: Combat Evolved was released for the original Xbox. The game was met with excellent scores, and established a large online community. Without a game like Halo, the original Xbox may have not done as well as it did. Halo: Combat Evolved has sold more than five million copies worldwide. Because the Halo series already had an established fan base by the time the sequel came out, it sold even better than it's predecessor. Halo 2 has sold over eight million copies worldwide. The already established fan base continued to support the Halo series when Halo 3 was released for the Xbox 360. Halo 3 has sold a little over eight million copies as well.
The point of the little history lesson above is to show that calling any first person shooter a "Halo killer" is silly. It's actually becoming quite ridiculous. The Halo series has a very large fan base. These fans have established a large online community, and love to play games of Halo 3 with their friends. Regardless of how much better you think a certain game is, they will be happy playing a game of Halo 3. There could be a huge news story on a respected gaming web site about how Killzone 2, for example, is superior to Halo 3 in every possible way. The graphics could be better, the sound could be better, the controls could be better, the campaign could be better, and the multiplayer could be better in the eyes of professionals, but at the end of the day, Halo fans enjoy playing Halo games. Video games, like films, are a matter of taste. Just because you like something does not mean that other people like it. People may not like the gun selection in Resistance 2 compared to the gun selection in Halo 3. You may think they are insane, but that is their personal opinion, and they are entitled to it.
If Halo 3 received very low scores because it was broken technically, then yes, a game like Resistance 2 would be a "Halo killer" because it's not technically broken. Aside from games that are plagued with terrible controls, and other technical issues, no games are really better than other games in the same genre. Everyone has an opinion on what is a good game, and what is a bad game. There were probably many times that you bought a game that got a high score from some web site, and you got it home, and didn't know what the fuss was about. Another example is a friend telling you how awesome a certain game is, and when you play it, you just don't feel the same. Everyone has a different perspective on what is good, or bad. People have been getting upset about people having different opinions forever, and it's quite silly. For example, Dead Space is a survival horror as is Silent Hill: Homecoming. Critics seemed to enjoy Dead Space more than Silent Hill: Homecoming. Does this mean that Dead Space is a "Silent Hill killer?" No, it doesn't. It means that in most critics’ opinion, Dead Space is a better game. Perhaps some people enjoy Silent Hill: Homecoming more because of the setting, and the storyline. Regardless, it's all a matter of opinion. An old school example is the classic Sonic vs Mario debate. Neither "kills" the other. Some people enjoy one, and not the other, or perhaps both.
In conclusion, Sony will probably never have a "Halo killer." When it comes to media, no one is ever wrong for enjoying a game. No one is ever wrong when they say that one game is better than another, because it's their personal opinion. Regardless of how many people enjoy the upcoming Killzone 2, it will never kill a series with an established fan base. The only "Halo killer" would be a prohibition of the playing of Halo games in general, and that may not even kill the beast. There would be an underground resistance of sorts. It's obvious that this is not an anti-Sony article. All of the games on the Playstation 3 mentioned above are excellent games. Are any of them "Halo killers?" Well, that's a matter of personal opinion.