I've only listened to the first one on your list, but it sounds alright. Remember, with a computer microphone you've got no control over any post-EQ and you only get one 'track', so you've gotta place your sound sources in the right spot. The singer should be sitting next to the guitar or even in front, unless he's screaming over an acoustic... And you should move the guitar back. It's got a bassy rumble from the guitar being close. Other than that, its a damn good cover, and I'm just nitpicking because of the onboard mic.

I've got a few covers on here, there's one 'Burden in my Hand' by Soundgarden. You might like it, but there's no video.