To get back to the racial discussion...
Quite to the contrary of the OP, I'm a little concerned that humans are a little too good. Or perhaps more accurately, that for someone who understands the math of the system, the number of race-class combinations that make sense are rather limited.
Let me reiterate the point about statistics that several other posters have made: a persistent +1 to a certain value never stops being valuable, whether you're level 1 or 30. This is not a matter of debate, it is a self-evident truth. Having a 5 percentile greater chance to do something or stop someone from doing unto you is always pure gold.
If we assume that combat will account for a major part of the dice-rolling in most D&D campaigns, we quickly realize that each class has one ability score that controls both the success rate and damage done with most of their powers. All of them, in fact, if they are chosen wisely.
This means that it will always be optimal to start with this main stat as high as possible at level 1, and increase it by +1 every chance you get.
What this in turn means is that you must choose a race that will give +2 to your main stat. The only exception that immediately springs to mind is dwarf fighters: the other dwarven racial abilities are so awesome for tanking, that not having max Strength can be forgiven.
If you combine this perspective with taking into account the usefulness of other racial abilities, the conclusion is that Humans totally bring the pwnage. The only other race that comes close for breadth of class options is Dragonborn. The rest of the races can all be good choices, but in narrower fields.
... Except Tieflings, who suck no matter how you cut it.
Edit: removed a faulty comment about level 28.