Both the opinion pieces and editorial choices used by all three are fairly extreme-left. There's ample bias, and the headlines and coverage are often unfair in my opinion. All three, however, often do good journalism, even if the pieces themselves are often chosen in a biased way. Buzzfeed (and Teen Vogue, for that matter), in particular, seems to be kicking ass at emerging as a new source of real journalism.

I don't think they are remotely comparable to more left-centrist news outlets, like NY Times, Washington Post, etc. These do real journalism and are close enough to center that their journalism should be respected by both sides, even if one could genuinely claim bias now and again. And they were, until Trump started attacking unfavorable coverage as "fake news". And now the tiniest incorrect detail seems to confirm Trump supporters' cries of "fake news! lies!"

I can't think of any liberal news outlet that compares to Breitbart. Breitbart is overtly racist and vile, and its commenters are similar. To be honest, it feels to me like we have "real journalism" smeared across the left-right spectrum from "slightly-right" to "moderately-left". A few sites like those you mention pepper the spectrum on the "very-left" end. Breitbart is on the "absurdly-right" end. It seems like conservatives don't have many things to choose from: centrist journalism that has stories similar to slightly-left news outlets, or hyper-partisan extreme- or alt-right commentary like Breitbart. Liberals enjoy more of a variety.