Best value, meaning fair price with consistent quality?Bushmaster.
Great quality, excellent customer service, and lifetime warranty? ARMALITE!
Those are my two favorite manufacturers.
Colt is over priced for what you get, has some odd ball part specs, and quality is sometimes hit and miss. I'm not a diehard Colt fan, there might be a preban or two out there I'd buy but for a postban rifle there are better deals or better quality to be had.
DPMS isn't bad but the majority of them aren't your standard AR15 configuration and aren't really a begginner AR15. I also consider Armalite to be the better deal even though they don't offer all the different variations that DPMS offers.
Wilson? Are you talking about Wilson Combat? Ouch! Talk about a solid thump to the wallet! What are you looking to use your AR15 for? If you're looking for a blaster for target shooting, the Wilson will be similar to a Ferrari seeing use as a grocery getter. If you're looking for a match grade AR15 I think you can find a custom upper assembly to put on a lower assembly that you built up that has all the quality of the Wilson if not more, but for an equal or maybe even slightly lower price. Check out Metalcraft Specialties
http://www.metalcraft-ar15.com/ , for really accurate rifles this guy has turned out some real nice AR15s where he's using top notch barrels, I've seen the results from some of the guns he's built and they are very impressive. They aren't blaster AR15s though, these are match grade barrels and should be treated as the gems that they are.
I'll say this as for what to stay away from, ASA and Hesse are both crap. Hesse is often reported to be hit and miss on quality control, there used to be a representative on the AR15.com boards but he got pissed by all the people complaining about their stripped lowers and he left that forum about a year ago. Then there is the wonderful Bob of ASA, he has been attributed as being the sole person responsible for the horrible ASA customer service, occasionally an ASA rifle makes it out the door and is a real lemon or not assembled quite correctly.
There have been people who have had good results with both ASA and Hesse but those people are considered by many to be lucky.
Once you get one AR15 you probably won't be able to stop with just one, that or you won't be able to keep it box stock for long.
By all means go over to the AR15.com forums and start poking around, you'll quickly find so many variations and makers out there that it's mind blowing. It took me the better part of 5 months to finally lay out the plans for who I wanted to build my upper assembly for my custom gun and what parts I wanted to use for my lower assembly.
Catch a gander at my ARs at my webpage if you're interested.
http://home.bak.rr.com/varmintcong/main.html