Well, there's a few flaws to your argument.

First of all, reviews take into account a reviewer playing through the (single player) game once, sometimes not to completion, before being rated. That presentationand initial impression weigh heavily in the review, whereas replayability and extra features weigh lightly. This is different for gamers.

KZ2 had a higher review score than Halo 4 - is anyone who is not heavily biased going to debate that it's as replayable? Halo games have always had a far greater number of multiplayer options, 1. and the average person who plays it will put far more time into the multiplayer. Reviews don't get to look into a crystal ball and say "as it turns out, playing Halo for 200 hours is a lot more fun than playing Killzone 2 for 100 hours". Reviews don't factor in other aspects, like the network. 2. Faster matchmaking? Local split screen? Not factored into reviews, generally. But it will factor into how often you play the game, and thus, how likely you are to buy the next in the series.

Killzone 1 wasn't popular, so it had little basis to make Killzone 2 a titan, whereas each Halo installment has been critically acclaimed, giving each successive installment giant shoulders to stand on.

In short, history will remember Halo 4 as the better game. Why? Because it is. If objective people could step back a year after a game's release, and factor in time played, overall enjoyment, etc., you'd get a true measure of a game's quality.

Pezus, lets not object for the sake of objecting. You know full well Halo has more longevity in multiplayer and the MP is what keeps it going years after release. You can have fast matchmaking without dedicated servers you know.