Yeah... umm... I'm probably the person most critical of U.S. foreign policy on this forum, and for the most part, I approve of what was done in Libya.
The distinction is not that it was a democrat instead of a republican president initiative, either. Let me lay down some of the actual distinctions for you, with Bush's war efforts as the closest point of reference.
Saddam and the Taliban were/are both horrible, yes. They had both done horrible things in the past. The people in Iraq and Afghanistan were oppressed. However, the U.S. was directly responsible for putting these people in power in the first place. It's kind of insulting to meddle in a country's affairs to horrible effect, and then expect that those people will welcome you to take another shot at it again later. Furthermore, the pretenses for the Iraq War, at least, were built on complete lies. While both regimes were still horrible, neither was in the process of doing anything extreme that warranted immediate forceful response. We acted like there was anyway, and in the process we have killed many times more civilians than either dictatorship ever did. If you follow the money, it's also painfully obvious that much of the war effort was designed to line the pockets of Bush administration officials, who had deep ties with the defense industry.
Everything was pretty much the exact opposite with Ghaddafi. To my knowledge, we were not at all responsible for his rise to power. Most importantly, he was actively attacking his own people. He had gone completely off the deep end of violent insanity, and was indiscriminately bombarding his own cities with artillery shells if he suspected them of housing any rebels. This was a large-scale bloody massacre in progress with no end in sight. We intervened with a minimal amount of force and collateral damage. Finally, our help had actually been requested. We didn't just charge in guns blazing like "Hey we heard a bad guy runs this place, so we're going to host a ten year violence party."
And yes, it's unfortunate that the U.S. doesn't intervene in more situations that obviously deserve it, and for obviously unsavory reasons. That's no reason to scold them when they actually do something decent.