USB mics and standard mics are usually built with the same microphone component, it's just that the analogue to digital conversion duties are handled by dedicated hardware, rather than your soundcard, in the case of the former. Build quality is typically identical. If your soundcard is utterly worthless, a USB setup may be a better idea, if not, it doesn't much matter.
Assuming you just have standard PC mic duties in mind, more or less anything should do, if you want real quality, you'll need to look into the sort of mic not sold for use with a PC.