The CETME is a Spanish version of the German G-3 or HK 91. They can be good rifles and are fairly accurate. Better than an AK-47, but not a tack driver like the AR-15. The only problem I have heard is that SOME of the Century Arms imports had a few functioning problems. These may have been the early ones, I am not sure. The price is ok, I have seen them here for $400 even. They are related loosly to the famed FAL rifle. The FAL imported by Century runs about $500. If ya want a scope one it, go for the FAL, it is easier to mount an optical sight on. If you like the reciever sights, the CETME is a good rifle.
As to the others that you mentioned, the AK was just too inaccurate for me, and I have never liked the SKS. The M-1 is great! You are just limited to the 8-round in-bloc clip. If this doesn't bother you, it may be the best choice for you. They are accurate, can be scoped, and are usually very reliable. I hope this helps.