CYMA AKs are probably the most reliable out-of-the-box guns out there. I've worked on probably close to a couple hundred CYMA guns, of many platforms, and I have seen some things I would have never believed could be done, and the gun still function. Full metal, real wood AKs, starting at about $150 new.
Now like I was saying, each brand has their strong suites. Their compression systems between all the more recent platforms, are impeccable. Not long ago, I had to lower the FPS of one, that out of the box(which advertised shooting 361fps) shot almost 460. I had to cut 5 coils off the spring to have it barely legal for the 365 limit where they were playing.
I could go on and on about my positive opinion on CYMA, but like many other brands, they also made LPAEGs, M4 platforms, which while still decent, were slightly weird spec for certain part fitment, and weak-ish gearbox shells.
The trash brands I am familiar with were SRC, Javelin, Double Eagle, just to name a few. And even then, it is really the SRC sportline, that were so cheap and widely bought, which brought upon their unfavorable reputation. Their non M4 models and higher end stuff wasn't as bad, but still not as great as what is available today.