A 4th-level commoner would probably beat a 1st-level fighter if you're using WBL. Using the standard 25 point buy (which is ridiculously weak but whatevs)...
STRENGTH: 16
DEXTERITY: 14
CONSTITUTION: 14
INTELLIGENCE: 10
WISDOM: 8 (rofl)
CHARISMA: 8
Do those stats suck? Yes. But that's the problem with the point buy system and 3e overall. This particular commoner will be the farmhand who wants to use a sword. Let's start with the basics.
HIT POINTS: The fighter has 1d10 + 2, or 12 HP. The commoner, on the other hand, has 4d4 + 8, or 19.5.
Advantage: commoner.
ATTACK BONUS: The fighter has a base attack bonus of +1. His Strength score gives him a +3 bonus on attack and damage rolls with melee weapons; his Dexterity gives him a +2 bonus to ranged weapons. The commoner has the same stats in this scenario, but his attack bonus is +2 (and he'll have masterwork weapons, as detailed below). On the other hand, the fighter will spend one of his feats on Weapon Focus because the PHB doesn't give him much in the way of options. Thus, the fighter is +5 (m) / +3 (r) vs. +6 (m) / +5 (r).
Advantage: commoner.
ARMOR, WEAPONS, AND WEALTH: These three are all tied together. The fighter is proficient with all armor and simple/martial weapons, giving him the edge in that department. The commoner, on the other hand, is going to spend two of his three feats on Armor Proficiency (Light) and Simple Weapon Proficiency because he's trying to be the fightingest farmer he can be. This still leaves the fighter with an edge. However, the commoner has significantly more wealth than the fighter. Now, I can't recall exactly how NPC wealth-by-level works, but I think it's roughly half of normal WBL. Normal WBL is 5,400gp for a level 4 PC, so I'm going to lowball the commoner's wealthy as being around 2,000gp. The important bit is that the commoner has enough for a masterwork weapon / armor. The fighter has but a meager 175gp. How shall we spend this?
The commoner is going to spend his final feat on Shield Proficiency, and he will use a heavy shield. He'll use a masterwork morningstar, which gives him reach. He will also use a masterwork light crossbow. He will wear a chain shirt.
The fighter is going to use a bastard sword (35gp), heavy steel shield (20gp), scale mail (50gp), and shortbow and arrows (31gp).
All things considered:
ARMOR CLASS: 19 (fighter) vs. 18 (commoner).
MELEE WEAPONS: +5 vs. AC (1d10 + 3) vs. +6 vs. AC (1d8 + 3).
RANGED WEAPONS: +3 vs. AC (1d6) vs. +5 vs. AC (1d8).
Advantage: It's something of a wash. The fighter has a fair advantage at range because he can reload his bow as a free action, allowing him to keep a distance between himself and the commoner. On the other hand, the commoner has an advantage in attack bonus and his AC is almost as strong as the fighter's. For now, I'm going to say the commoner wins out.
MISCELLANEOUS: The fighter has the advantage in his feats. He's going to spend his feats as follows: Improved Initiative (always good), Exotic Weapon Proficiency (Bastard Sword) (why not?), and uhhh....Weapon Focus (Bastard Sword).
The fighter has a big advantage here because Improved Initiative is a really great feat. The rest of it...well, using 1d10 instead of 1d8 is okay, and Weapon Focus is the default "hurrdurrrrr fighter" feat.
Overall, here's what the statblocks look like:
FIGHTER
HP: 12
AC: 19
Sword: +5, 1d10 + 3
Bow: +3, 1d6
COMMONER
HP: 19.5
AC: 18
Morningstar: +6, 1d8 + 3
Crossbow: +5, 1d8.
Who wins the fighter? The commoner, most likely. The only scenario where the fighter wins is if he can kite the commoner, and that's unlikely to happen. The fighter is more likely to act first, but the commoner is liable to outlast him. I don't feel like calculating average damage per round. The fighter's is slightly better (+1 average damage), but the commoner has more HP, so I'm going to put my money on the commoner.
Now, once the fighter hits level 2 and gets a few more coins in his purse, he's going to beat the tar out of the commoner, but for level 1, they're fairly evenly matched.
I'm okay with this.