I used to have the same probs with basslines mate, they all used to sound too cheesy and commercial, not the aggressive techno sort at all.

It's trial and error with synths, pick one you like and feel comfortable using and then learn how the waves, modulation (very important) and frequency cutoff affect the sound.

It's all in the modulation with synths, and a sound that can sound terrible with the frequency cutoff open can sound amazing with the cutoff nearly closed and a bit of resonance. All this trial and error will help you devise a method for getting the sound you want.

Other things to try, mix a synth sound with percussion sounds (snares are good) playing the same bass melody, and then group the result and close down a cutoff filter over the lot of it.

FM creates good modulation with bass, so try a bit of that as well.

The synth that taught me the most about bass is the V-Station, I highly recommend trying that as a starting point.