I would stake my Echo 1 could go toe to toe with a classic, and for the price, thats the better rifle.
G&G may make a fine M14 but AZsarge is right, they can't make an M4 thats up to par.
KWA G36 is extremely nice, and I would assume the M4 would have the same reliability, even if it wobbles a bit.
I like the CA metal body and pseudo- trades, but I haven't had the best of luck with CA, and judging by the function I have seen, there M4's, un-upgraded, are average, though still better then a TM.
The new TM SOPMOD has me highly interested, but, unless I get my hands on one, I would advise you to steer clear of TM, you can get a better bang for your buck elsewhere.
Just my findings based on experiences I have had and have seen.