Here's why I think that they are the most powerful.
First off they get 600 hp now as opposed to 550 before, that's a lot of hp for classic age. As well they get pretty good attack, and decent armour (40,50 I believe) as well as the all important crush damage. Their special attack can* rock, I did some tests on it tonight and here is what I found.
I surrounded 1 cyclops by tons of ulfsarks (so he wouldn't die too fast The downside to this awsome special is rather large, It seems to be quite random as to the direction the cyclops actually throws the enemy unit. If you were able to control this special it would be absolutely amazing (and possibly overpowered), but if anyone does know of a way please post it here so we can use it to defeat those evil norse players hehe. In conclusion I really think that cyclops is the most powerful unit in classical, and can even be used very effectively in the later game due to the fact that he gives an insta kill to any normal unit (his special doesn't work on MU or hero's of course), has high hitpoints, and with his elite upgrade from the temple (which is quite expensive since these guys are impossible to mass early on) does a lot of damage.