Hard to say. That Realtek garbage is certainly not the best thing to use for quality audio. Without a doubt SOME of the problem may be coming from that.
Level mismanagement may be the culprit. Are your recording levels too high or too low?
Are you sure you are recording at least CD quality, 16 bit, 44.1 kHz?
Poor quality connections could contribute. Poor quality microphones could contribute. Grounding problems could contribute. Cheezy playback equipment (amps, mixers, outboard effects, etc.) could contribute.
All we know is that you're recording through a cheap soundcard. That's all the info you gave. It's up to you to know what you have connected to what, and research articles about your equipment, connections, recording techniques, level management, etc.
EVERYthing that passes an audio signal has some inherent noise. If the first item in a chain makes the greatest amount of noise, everything after that will make it worse by adding more noise, or amplifying the noise.
If you have a combination of things, like bad level management going through cheezoid equipment, there is no way to NOT get bad audio.
Research all the stuff mentioned above, maybe even find other useful forums, and try to narrow down what YOU think may be the problem. What you are asking is basically the same as someone saying "I baked a chicken, and it doesn't taste right.....what did I do wrong?"
I dunno. Did you burn it? Did you stuff it with cinnamon? Did you baste it with anchovy oil?
A better audio interface will definitely help, but if all the other things aren't considered, you can still make lousy-sounding recordings. Someone who knows nothing about equipment and techniques can walk into a multi-million dollar studio and create sonic waste. Conversely, someone who has insight may be able to make very good recordings out of very primitive equipment.
The answer lies in what you will learn