Love the FN-Fal's and Galil's (Ar model in 7.62). They both posses very good reliability and human engineering. Both are accurate for semi's and very comfortable to shoot as I can get a comfortable cheek-weld. Trigger's not great but not bad either. Both have excellent balance.
Hate the HK-91 series. Poor human engineering, reliability (fluted chamber hates sand). Worst trigger pull of the bunch. Worst front sight- the hood way too thick, the brittle front sight plate too wide, leading to poor accuracy. Poor balance, weight shifted more towards barrel end. Awkward for me.
Love the human engineering of the M16 series, just hate the fact of direct exhaust gasses contaminating the rotating bolt directly.
Hate the human engineering of the AK47 series. Love the reliability which is the best of the bunch. Worst accuracy of the bunch.
The above is my opinion only based on the samples that I've fired. I really like the 7.62 NATO round (I like the fact that I don't need to buy two different calibers of ammo to shoot my L1a1 and Rem 700 PSS. Wish I had the opportunity to own a Galil AR762 (I did own a Galil AR223. Was my all time favorite except for the caliber.)
Gun models are like car models. Ask a hundred different enthusiasts and will get a hundred different responces.