The thing with Ryze is is that it's about 10 times harder to counter him than it is to play him, which is what makes him so unbalanced. As a champion he is indeed balanced, but the skill it requires everyone throughout the team to have to counter a single button bashing champion that a monkey can play properly is simply ******ed. Yes, Anivia can deal a large amount of burst as well, but it's balanced because it is a lot harder to dish out damage as Anivia, whereas Ryze can simply do R, W, Click, Q, Click, E, Click and you're down, no need to aim anything, no need to conserve cooldowns, there's just no thinking involved.
Yes, you can counter Ryze and this leaves him low-tier at high-top tier play, but in low-mid tier play it is too easy to dominate as Ryze, because the champion itself requires 0 skill to play as and it is hard to counter when lacking certain champions, or when having too many melee champions, which will be the case occasionally in low-mid tier play (which is where most people play, mid tier, you know, average).
Personally, I think Ryze's damage needs to be cut, but he needs some more utility and range to make up for his damage cut. A lot of you are saying "Ryze will only one-shot you when fed, just like any carry", and this is true, however, all other physical carries have low base damage, whereas Ryze's base damage will take you to 20-40% all by itself, making it easy for him to get fed unless everyone in your team plays well.
Once again, the imbalance in Ryze is the skill required to play him well versus the skill required to counter him, not the champion itself.