It's because you're going from an amp output straight into your soundcard. If you want the actual sound of the amp, you need to mic it, and then you need an interface that will provide the preamps for the microphone and send it the proper way to your computer.
Normally, people do this with actual mixers.
If you don't want to physically mic the amp, then your option is DI (Direct In), but you don't use the amp for this... you simply plug your guitar straight into the instrument input of your soundcard and record the weak, crappy signal, then run that signal through an amp simulation program in your project.
This isn't the end-all rule or anything. I'm just letting you know why your approach is turning out sh*t.
Also, Creative Soundblasters are for consumer-level gamers. It's not for audio recording. If you're serious about recording into the box, your first purchase is going to be an actual audio interface. There's a reason they exist, and it isn't to just make you pay more money.
Anyway, it sounds like you should do some Googling to learn the basics of audio recording for a home studio. Don't worry, there is multitudes of information out there. If you have any questions about it, don't hesitate to ask.
But please do use that resource first.
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