As noted, 4E wizards are controllers, not strikers. Their purpose is to to control the battlefield, not dish out huge amounts of damage.
Having said that, though, consider that the ranger above is doing 20 average damage to a single target. If the wizard above chooses an area-effect at-will power (say,
thunderwave), they could be dishing out an average 7-8 damage per opponent within the area. If they hit more than 2 opponents, they're actually doing more damage than the ranger. Wizards have access to many burst and blast powers, which means they can (in aggregate) be amongst the most damaging members of the party.
If you're looking for "single target" elimination, you want to look at
effects rather than raw damage. The 1st level Daily Power
sleep is an example of this. Any enemy you hit that fails it's initial save becomes helpless, which means automatic critical hit from your allies when they coup de grace it. Your wizard might not be the character that deals the killing blow, but he's effectively the one that eliminated the opponent.
...but again, the main purpose of the wizard is to prevent the enemy from making the best possible use of their own attacks against your party. You have walls and zones to shape the battlefield... you have effects that move, slow and daze enemies... you have summoned creatures that can get in the way of enemy attacks, and fight back... the ranger, for all his damage, has very little of any of this.
Some final notes, purely in regards to the examples given above...
- both characters would have benefitted from a higher Int/Dex (start with an 18 at least, after racial adjustments)
- the wizard would probably have been better off with a wand rather than a staff, if their focus was on damage (more accuracy, rather than more defense).
- magic missile, while a good power, dishes out less aggregate damage than an at-will area attack like thunderwave, assuming you're fighting multiple opponents each fight and can position yourself well.
- you definitely want to look at the post-errata magic missile, which hits automatically (especially as it sounds like your attack bonus is on the low-side for a wizard - many wizards will have a +5 Int after racial adjustment, implement expertise for +1 attack, and the wand of accuracy class feature).
- look at other sources for feats. PH2, PH3, Arcane Power, and the new Essentials releases all have good feats for improving wizard damage and accuracy. At a minimum, take Implement Expertise (+1 attack with implements). It's more important for a wizard to hit, than to do damage... as they usually have cool effects triggering off their powers.
- check the WotC website for errata, or pick up Heroes of the Fallen Lands. Wizards in particular received a do-over in Essentials. Several of their powers have been revised or improved. The most significant change is that msot wizard encounter powers now do damage even if they miss, which is a big improvement.