Where the wizard has his moments of glory it is against a larger number of critters. So when that chain lightning fires off it does have devastating effect in that he can really spread the damage about. Against single foes that are designed to be a reasonable challenge the fighter and paladin do just fine in damage output in comparison to the wizard in the group.
Your Wizard is suboptimal. PF Wizards are almost identical to 3.5 Wizards, but even more versatile in most cases. Wizards who spend their spells blasting stuff are balanced with other classes, because they are only using a fraction of their potential.
Full casters in PF still dominate by summoning monsters that make the fighters redundant, casting utility spells that make skill monkeys convenient rather than necessary, and controlling the battlefield so that everyone else defeats monsters 200% more efficiently.
On the other hand, Pathfinder adds several classes with 6 spell levels; except for the summoner, they are all much better balanced with fighters than the full casters. It's pretty reasonable to run a campaign where full casters are banned, and then the spell caster problem is much less pronounced.