==Warning, Old post==
I like them both, but Halo 3 gets my vote.
Like Viper was saying, and this is what I have argued to my friends, it is bullshit how I get into a game and the people who are better in skill have an unfair advantage: better guns. This makes it not fun at all for the people who are not very good at Call of Duty.
The realism in Call of Duty is too a point where it isn't fun. I mean you die so much it just gets you pissed off. I have been in many party's where I am playing a game and the people in my party are so pissed off from dying. These are legit players too. The game is based too much around which gun you choose. This is the main reason MLG still prefers Halo 3 as its main competing game.
Don't talk about the Graphics in Call of Duty are better then Halo. It is not merely a statement, but a fact that the Halo Engine is better. Call of Duty has been using the same engine with small modifications since COD2. This includes the new game CODWAW. The Halo Engine was almost completely wiped from Halo 2, and they basically re-wrote it for how powerful the Xbox 360 was compared to the original. The only thing I don't particularily like about the Halo Engine is its ellipse rendering ability, and sometimes on round objects it will seem a bit pointy as you can see how the polygons make up the object.
Now, in terms of the best engine, it's hands-down Unreal Engine 3. Games that use this are Gears of War, Mass Effect, Turok, Bioshock, and more.
http://www.youtube.com/watch?v=-m4pe6UAS2M
If I'm playing Halo, and I start getting shot from behind, I can possibly get out of the situation and kill the kid because I'm a better player then him. In COD, it's basically whoever sees the person first gets the kill, regardless of skill.
Also, the thing that pisses me off about Call of Duty. I'm not an exceptionally good COD player, but I play enough video games that I knew what I was doing when I first tried it. Better then most level 35+. However, despite that I am better then those kids, they can still destroy me because they have better guns. Nothing like getting killed by people that suck because of an unfair advantage.
Use facts, not useless fanboy garbage btw
Old thread
http://www.sythe.org/showthread.php?p=4561859