I'll be glad to answer your question. The best AKs are the ones manufactured in a European or Asian factory that made the AK military rifles for a particular country and imported into the US with no modifications. These are in two categories; pre-1994 ban and post-1994 ban. The pre-bans look pretty much like the military rifles and the post-bans are sporterized but still the same inside. The post-ban 'sporters' were only allowed in for a couple years until they banned them too, so there aren't many around. Pre-bans are now about $1800, but there are Chinese and Hungarian post-bans from about $500 up. To make these look like pre-bans, they have to be modified to meet the requirements of a law called 922r and can only have so many imported parts from a list of major parts. The other parts have to be USA-made. All newly-made AKs you can buy today are kit guns, made in various garages and shops and are 922r compliant. There are exceptions, like all-USA AKs which have no restrictions but don't seem to be very good either. So if you now want to know which is best out of what you can buy 'new' now, it looks to me like the shop-converted Saigas are pretty much on top of the heap."
Nice reply saxman1. I'd like to add concerning the two receiver types. After the initial run of military Ak47's which used a hybrid stamped/milled receiver, milled receivers became the chosen receiver type. Milled from a solid block of steel as opposed to a folded sheet metal stamping. Around 1957 the Soviets found ways to address the problems arriving from the stamped receivers and the AKM became general issue. The stamped receivers were more economical to produce and resulted in a slightly lighter rifle. The AKM also fielded other changes such lighter barrel, different stock angles and sights. The Chinese converted to stamped receiver Kalashnikovs without Soviet help and their modernized AK resulted in a stamped receiver AK47, same heavy AK47 barrel, AK47 stock angle, sights, and a slightly thicker 1.5mm receiver instead of the 1mm Soviet/Eastblock standard. Also the Yugoslavians went their own way in a modern Kalashnikov incorporating RPK (squad automatic) receiver and trunion parts. These variations don't mean much when considering a semi only AK as any of the designs are more than capable of semiautomatic fire. Saxman is correct concerning the general state of US produced Ak's and some not being that good. The good news is the design is such that given a good receiver, and the receiver is the heart of any firearm, a small shop or even the fine folks "crafting" AK's at Century Arms seem to be able to produce a decent 7.62 cal. AK. Most of the 5.45 cal seem to be fine but sometimes there are a few design issues that can plague the 5.56 rifles. Again Saxman is correct that the converted Saiges tend to come out nice. Also the products of Arsenal in LV, NV are world class, expensive but very excellent. Also keep in mind the lowly WASR, a Romanian single stack rifle imported and "fixed" by the CAI craftsmen offers a combloc chromed barrel and comblock receiver along with an entry level price. The mag insertion can sometimes be rough and there have been issues of canted sights, even the WASR is known to be reliable, and more accurate than 95% of the people that shoot it. As others have stated, there's a wealth of info here and other places. The Kalashnikov family of small arms is a fascinating subject that you can spend years studying.