[cerberusss]

iTerm -> Preferences -> Profiles tab -> Colors subtab.

You'll see two columns of options. The left column is titled "Basic Colors", the right is titled "ANSI Colors".

Under Basic Colors, click the color next to Foreground, and a color picker appears. Slide it to the lower-left: bright white.

Now it should be fixed. But if it didn't, repeat the same procedure for the White that's at the bottom of the column ANSI Colors.

[TurkTurkleton]

There's also a setting that controls the thickness of font strokes, independent of color. I forget exactly how it's labeled (not at my Mac right now), but I remember it's a dropdown with combinations of options for using thin strokes on dark backgrounds and/or Retina displays. I believe it defaults to using thin strokes on Retina displays. I believe turning this off will make font rendering identical to Terminal. Either way, I think it looks better turned off, even on a Retina display.