The AR market is HUGE, with as many companies (possibly more) making AR platform rifles as companies making 1911 platform pistols. The overall price range is enormous, so it's tough to say which is "better" or make a recommendation without an idea of $. For a grand +/-? Bushmaster makes a nice rifle. The A3 and MOE models are very good; reliable, cost effective, etc. I've heard that the Bushys pre-move to Ilion, NY are better than post-move, but I can't say one way or another. DPMS is a bit lower end from Bushmaster (although both are owned by Cerberus, which also owns Remington and Marlin). Colt is the standard, but tough to find. The hot-rodded ARs can get VERY pricey, so depending on budget, they may not even be in the discussion.
A big factor is personal preference. Do you want a telescoping stock or fixed? Rails for stuff? Flat top or iron sight? Carbine M4 style or traditional AR?