Well, naively optimized wizard at 1st level might be in trouble, since low level blasting is horrible. T5
Moderately optimized wizard has Enlarge Person, by which he turns himself(if desperate) or the Fighter into a killing machine. He'll prepare one of those.
Against massed mobs, he has Sleep and Color Spray. He'd prepare one of those too.
As general utility, he'd then prepare a Silent Image(which'd buy a round of time or three)
Tactically, if the fight is against a mob, he'd move to lay down the Sleep in the opening salvo, remaining party members engage NON SLEEPING foes. Given that the likely mobs at level 1 are half or quarter HD, it'd most likely wipe out half the opposition. In subsequent rounds, depending on enemy AC, he may use his crossbow(he's only slightly less likely to hit than the rogue anyway) or Daze cantrip. Once all active does are down, proceed to CdG the sleepers.
Against a powerful individual, avoid risky gambits like the save or lose. Instead, Enlarge the fighter, and while he engages the opponent, fling Daze and Flares around to buy time. It wouldn't take much. Alternatively lay down the Silent Image as a backup.
The above set of moderately optimized core, level 1 spells(which note, most wizards will be able to have and to spare, as they get a lot of spells at level 1) allows it to perform as a T2-3
Fully optimized wizard would do much the same, except possibly doing tricks like selling the spellbook to buy stuff, which can get you to T1, but also smacked with a rulebook.
Contrast
Level 1 fighter
Naive optimization: Get a sword, shield, weapon focus and probably power attack or quick draw. Probably medium armor, since he can't really afford good heavies. T5. He won't do much damage, and his AC isn't that much better that he can count on not being meatpaste in the opening round.
Moderate optimization: 2H reach weapon, best affordable armor, power attack, combat reflexes. T4.
Full bore: Maybe a lance, a horse and power attack. Still T4.