Two things I think should be mentioned.
First off, AC is horrible. It's not only the worst scaling defense in the game, it's also the most binary. It's a yes or no "do I take damage," and it didn't scale at all. Unless you were a front line fighter, you were really typically better off going for things like stoneskin or displacement or other such effects. Now, as the game progressed, this got fixed in a number of ways. Tome of Battle gave martial classes several potential abilities to help their AC and their skills, so they wouldn't be ironically the least defended people in the game, with abilities that would give you skills to saves or AC, or even your attack bonus to AC.
Secondly, it's interesting to see how baseline stats have been going up and up with each edition (at least since 2e, which is the earliest edition I've played).
In 2e, having a 16 in your main stat gave you an experience bonus, and the standard of character creation was rolling your stats, though - at least from what I saw - the most often used method was 4d6 drop one. Races would have +1 and -1 to two stats. Mechanically, it was because dexterity was how you figured all rogue abilities, strength was for attacking and lifting gates/bending bars/other feats of strength, intelligence governed your ability to potentially learn spells, etc. What it ended up meaning was that characters had fairly average, if random, statistics, and that thieves were nimble and quick, fighters were strong and powerful, wizards were knowledgable and smart, clerics were wise and understanding, etc, etc. Having an 18/00 in strength was a big deal, having an ogre's strength meant literally having the strength of an ogre.
In 3e, the push was made towards point buy, with 28 being the standard. Because statistics were altered to give a +1 modifier for each even all around, races gained +2 and -2 to their stats. Lastly, stats are no longer static - they rise as you level. Mechanically, the lines of what stat can be used was blurred a bit, with things like Weapon Finesse giving dexterity to hit, and skills were given to everyone rather then different classes having different subsets of skills, though "class skills" were kept. What this meant mechanically is that most characters were somewhat above average, perhaps with one skill greatly increased, or two skills fairly increased. Rogues were greatly more skillful then fighters, but overall classes are blending together, and stats are more abstracted.
In 4e, point buy reigns supreme, and the stats are much higher. Stats go to your various attacks, your defenses, and your skills, which can lead to oddities like there being no class that wants high dex and intellect at the same time (in fact, my favorite stat combo tends to be punished

). Characters tend to have strongly above average stats, with one incredibly exceptional stat, or two very potent stats. Furthermore, players do not have lower then an 8 in any stat, and that's only in one stat. Skills tend to be more even across classes, along with a reduced number of skills. Stats are very abstracted at this point.
It makes me wonder what we'll see in any future theoretical editions, at least as far as stats go.