Opting for a shield fighter vs. a (pre-errata) battle rager fighter? Opting for warlock vs. a sorcerer? Opting to have any bracer slot item that's not iron armbands of power vs. iron armbands of power? Any weapon that is not bloodclaw vs. a bloodclaw? Numerous powers which get passed again and again vs. those that get picked again and again?
Out of everything in 4e, there are probably only 6 things that I've ever thought were considerably more powerful than all other options. They are pre-errata battlerage vigor fighter, iron armbands of power, bloodclaw, rain of blows(pre-errata), veteran's armor(pre-errata), and the warlord power that allowed you to switch initiatives with other people(pre-errata). All but 2 of these have been errata'd. And Iron Armbands are kind of iffy. They are still close to being balanced.
So, if you remove that entire list as choices, I think you'd be hard pressed to find something else that was as overwhelming as you say.
I'd be willing to sacrifice that bit of variety if it meant that everyone is awesome, but that is decidedly not my experience in 4E.
Wow. Even the difference between the weakest option and best option in 4e is still closer to the difference between two fighters in 3e rather than the difference between a fighter and a wizard.
I'm willing to admit that the 14 Cha Warlock who takes all non-combat feats va the 20 Cha Sorcerer and 16 Dex who takes all of them and has a +1 weapon is not fair balance. It'll suck to play that Warlock. On the other hand, the difference between them is:
Warlock: +2 to hit for 1d6+2 damage
Sorcerer: +7 to hit for 1d10+9 damage
At 30th level, as long as they both keep putting all their points into their primary and secondary stats and get appropriate magic items(no matter which ones they pick), the difference isn't going to grow that much:
Warlock: +27 to hit for 1d6+12
Sorcerer: +34 to hit for 1d10+24
Which is a pretty big difference. But the Warlock still gets a bunch of secondary effects from their powers. They are immobilizing people, giving them minuses, and some other effects that the Sorcerer isn't doing. Some of their powers do half damage on a miss or have an effect on a miss. When targeting a weak defense, the Warlock hits a level 30 solo on a 15.
It is, however, nowhere near the difference in 3.5e between the Fighter who put a 14 into their Str at level 1, chooses all non-combat feats, and multiclasses for role playing reasons into things like bard and rogue and the Wizard who put a 20 into their Int at first level and chooses all combat oriented feats, and optimizes their multiclassing into useful PrC.
I can't even estimate the exact numbers due to the number of variables involved. But it's fair to say that the fighter involved would need 15s to hit most enemies at level 20. The Wizard either doesn't require attack rolls or hits on everything but a 1. The Fighter would do approximately 1d6+9 points of damage on an attack. The Wizard would be doing about 20d6, twice a round, while flying, invisible, and nearly immune to attacks. That is, assuming he doesn't just kill the enemy outright with his first spell.
To even compare the two is nearly incomprehensible to me. There is enough variety in characters to have a difference between the best and worst characters in 4e without making the difference so great as to completely eliminate the worst person from the combat.