Some people got it, some don't.

I haven't seen any of your work yet so I really don't know what verdict to give. But maybe you draw too generic, like The-Switcher does. You need to get a style of your own.
Or maybe you don't like the style you *do* have. In which case, carouse the Net looking for other artists that have styles you like and try to mimic them. That's what I did, and I couldn't be happier... Well, that's a lie, but you get the idea.

I admit that I have being inspired from Venomark, fatsatan, The Switcher(his fake pics), X, ... And many others, but I try to be original and I think I made it, I think I have my "own" style now.

Like Ramspoon just mentioned, Some have it some don't.
I never took any artistic class except the ones at school.

Have you actually only been drawing for 3 years, or is it just three years since you started taking classes? Me, I've been drawing since I was 3. That would make about 25 years. I've only taken about 5 classes in all that time.

To be honest though, I only really started to improve in drawing people the last 3-4 years. Why, because I realized the way I'd been doing it wasn't getting good results so I started studying again on my own. I was wrapped up in CGI so much I had little time for anything but concept sketches. Most likely though I just didn't practice enough.

That last point is probably the reason, you can study every book on art there is but practice is what makes you improve.

There could be something else, maybe you don't really like to draw. To alot of people it's more of a chore than a joy, like me. Let me explain. I am constantly coming up with ideas, the problem is I'm lazy and always distracted. Some of you ADD types may know what I'm talking about. Actually giving an idea life seems to me to be one of the hardest processes for me not because it is hard, but because it takes so freakin long. Therefore I get distracted on something else and nothing gets done. You notice I haven't posted that Kitana pic yet, that's because I'm still working on it. Granted it's a difficult piece (probably too difficult) but I should've been done right now. In the meantime I'm: reading two different series of books, working on a documentary of my Grandfather, finishing an independant movie, studying for my CCDA, CCNP, and MCSE certifications, and teaching network engineering at two different colleges. This is on top of four video games I'm playing right now, the band I play in and a comic strip I'm trying to market. And none of that stuff gets as much time as my wife and my kids. Put it this way, I should be finished with the "drawing" portion of my picture today, then comes the coloring so it might be awhile.

What I'm saying after all that mess is it could be that you want to draw real bad, but don't really invest the proper time for it. For me it never seems to get easier, but that's probably because every picture I do is more difficult than the last.

Blast, I just realized I've got to finish concept designs for my new cartoon Space Bums.

He who will never be free of the ravages of creative thinking
Wyatt

Practice, practice, practice.

I made my first drawing on computer over a decade ago, and my first drawing on paper was even more than two decades ago.