The weapons in Halo 4 are just like those in real life. Not in the sense that the real world has superheated slug throwers (it does not) or even laser weapons (I wish!) but in the sense that weapons in both Halo 4 and the real world have an effective range.
That is to say that after a certain range, a weapon isn't all that effective because of dispersal (bullet spray), among a variety of other factors. Given that the weapons in Halo 4 aren't as accurate as those in Quake or Doom, and are heavily impacted by dispersal, it's to be expected that they can be terribly inefficient at various distances, or vice versa.
To that end, a Halo fan and redditor ZenRain has put together a helpful infographic with each of the weapons in Halo 4 and their effectiveness at various ranges in meters—instead of feet or yards, because the UNSC doesn't much care for archaic systems of measurement.
To no one's surprise at all, weapons like the Suppressor, Assault Rifle and the Storm Rifle prove to be next to useless at distance beyond 5-10 meters and are best suited for close range encounters. Single-shot and burst-fire weapons like the Battle Rifle and the Light Rifle are superb for mid- to long-range encounters.
The list takes into account every pre-selectable weapon, including all primaries and pistols. It doesn't take into account specials like the Incinerator Cannon or the Spartan Laser, which are more powerful than anything you'll load up with when you spawn, anyway.
Take a look at the list of weapons and their effective ranges below. Full credit, once again, goes to ZenRain for putting this thing together. Go give him some reddit gold.
