I Don't Get It. Halo?

[Warjack Prime]

So I picked up an Xbox 360 for Christmas and bought a handful of games. I just finished running through both Gears of War games and wanted to try Halo 3. I've played several other 1st/3rd person shooters on the PS3 before, including Resistance, Resistance 2, Killzone 2, MGS4, Uncharted, Uncharted 2, Dead Space, Modern Warfare, Modern Warfare 2, and Battlefield Bad Company.

I don't get Halo 3. Should I have played the other two first? I was really expecting a top of the line shooter but I find it completely annoying to play. My main complaint is the fact that it seems like all the enemies are really far away from me for the most part and I can't zoom in any gun except for the sniper rifle so it seems really hard to accurately hit things. Second, it almost seems childish. Some enemies yell things in a high pitched voice, such as "I'm going to get you, you jerk." What?

Mostly I just find it hard to shoot since I can't zoom in and the enemies always seem to stay so far away and run around. They actually dodge my bullets. Am I doing something wrong? I want to like this game and I'm still on the first level (I think) and I don't want to quit.

Man I hope Halo 3 ODST isn't like this. It's not fun at all.