Balanced, sure. But by what definition? Enough to prevent one class from overshadowing another. And I think most versions of D&D achieved that. It has never been my experience that one class routinely overshadows another. I've seen players overshadow each other, but I've seen that done with all sorts of class combinations, not just caster over non-caster.
Just because you haven't seen the problem doesn't mean that the problem does not exist. Extrapolating your particular group onto the masses isn't terribly useful.
After all, I have seen classes totally dominate the game. I've done it as well, the powergaming muchkin bastard that I was once upon a time.
So, let's leave our dueling anecdotes at the door.
One thing I am surprised about is the results of the poll. Given the amount of flak 4e gets for trying to achieve character balance, I would not have thought that Option A - All Balance All the Time would be so far ahead of any other option. There really isn't very much support for the classic style of balance across multiple levels.
The problem is, in addition to wizards and clerics gaining access to spells so easily (well, clerics always did) is the HUGE BLOAT of spells. Expert D&D had what? Six or eight (I forget which) spells at any given level. That's it. You had a couple of attack spells, a couple of utility spells and a couple of defensive spells.
The casters couldn't dominate the game simply because they never had the options to do so.
You want to have parity between caster and non-caster? In 3e, make all casters use the Sorcerer Spells Known table and make them spontaneous casters. There, end of problem. Fighters and fighter types are now on par with all casters.
It's the bloat of options for casters combined with the idea that "It's magic! It can do ANYTHING!" that has made this problem. Take that out of the equation and you achieve parity across the classes.