As a note, these comparisons also depend on the particular classes involved.

For example, if the wizard's two first level spells are mage armour and magic missile, the wizard will not be dominating anything. Comparably, if that same wizard prepares sleep, then that wizard will rather smash up a particular encounter. Also, the general consensus is that wizards who are essentially warmages tend to end up at the lower end of the curve on most levels.

Similarly, a fighter who has a relatively weak build is less likely to be as potent as other fighters, regardless of level.

Personally, extremely low-level games (1-3) tend to be poor analyses of classes, especially level 1. At level one, a fighter's 8+con hit points have to go against the enemy's 1d8+str damage. Throw in the fact that fighters tend to be up front, and you get very frequent deaths in either party.

Extremely low level D&D tends to be exceptionally fatal regardless of your class. The frequency of one-hit drops tends to, at least in my experience, make your defensive ability not terribly relevant there - you've got to be a dwarven barbarian to reliably soak one hit from an orc, and kobolds and the like come in groups or pairs.