I've found that the wizard is just fine. His dailies tend to define the encounters in which they're used, much like Lead the Attack, except with more explosions.
We're at level 9. If we go through 4 fights in a day, one fight will be defined by the wizard exploding off ~20% of the enemies' hit points in the first round of combat. Another will be defined by the wizard dividing the battlefield in half with a giant wall of fire, and then everyone spending the entire fight throwing enemies back through it whenever they try to get out. And another will be defined by the wizard driving a ball of flame around the battlefield like a bulldozer.
In general, people who don't like the wizard tend to view his damage as being too low, and complain that he's only worthwhile when you have hordes of weak enemies. I think this is a misconception: area of effect damage is recalibrated in 4e. You're not going to slaughter foes left and right with it, but it does tend to do more damage than regular attacks. For example, an attack that hits 60% of the time deals 1d6+8 damage (level 9 wizard, 20 Int, +2 implement, +1 feat) to two targets has an expected damage of 13.8. In comparison, with similar stats, Reaping Strike with a mordenkrad dealing 2d6+8 damage (5 on a miss) to one target is dealing expected damage of 11.6 (thats with one more feat for the fighter, for the record). The fighter, of course, marks his foe, which has a lot of value. But so does damage.
If you look at total damage instead of damage to an individual enemy, even the spells widely viewed as sub standard are pretty good: Fireball is popularly viewed as a disappointment in 4e. But if you attack 5 enemies with it (very plausible, since you'll hold off on casting it until you can get most or all of your foes in the 7x7 explosion), have a 60% chance of hitting, and deal 3d6+8 damage on a hit, half on a miss, you'll get an expected damage of 70. I'm reasonably sure that's the highest level 5 daily power expected damage available in the game that doesn't involve damage over time. Now, if you're doing that at level 9 like our wizard is, your expected damage versus an individual foe amongst those five is 16. This isn't going to make any of them weep, they probably have 70 to 90 hp. But viewed as a whole, its a lot of progress towards winning the fight.