Sorry, I don't agree. He may be the man of tomorrow, but what he fights is the never-ending battle after all.
I agree that Superman shouldn't be 100% defeated by Luthor every single time (has it ever happened anyway?) and he could also be victorious from time to time, but I will always be in favor of more ambiguous notes rather than flawless victories. A winning character will never be as interesting as a sympathetic one who never surrenders.
I wouldn't take the Golden/Silver Age so much into account, either. Superman's world in those stories was so naive and simplistic that IMHO it is not really comparable to DCU as we know it today. I am not saying that current DCU is the one which I'd personally hope for, just that it's a different type of storytelling from the one in the classic stories.