Confidence bro. I don't personally believe in "good" or "bad" guys. Way too arbitrary; There are guys who have confidence and get chicks and guys who don't. Also, "nice" guys (as they are often called) are generally too nice. Chicks don't want a guy to cater to their every whim and follow them around like a sick puppy. Live your own life. Be confident and comfortable with yourself so you don't feel the need to put on a facade of "nicety", which really just reeks of "desperate" and "too available".
Now this isn't to say treat women like sh*t. Keep a strong foundation of morality, that is a good thing. Don't be afraid to make mistakes, just learn from them; Just be yourself. Call them on their sh*t, and show them you aren't afraid to cut to the chase. Be spontaneous and unpredictable, yet romantic and mysterious enough to keep them wanting more. Don't mistake being nice with pining and cow-towing, they are not the same thing, at all.
Also, just because you play the field doesn't mean you are a bad guy. Practice. Practice. Practice. Practice flirting, conversing, picking up body language, and getting numbers/dates. This will make it easier to meet women. If a chick is pulling you along on a string to hang out or date some other guy then stop talking to her for a while (this drives them nuts when they think they have you around their finger). Find the chicks that like you for you and be selective and deliberate.
Which brings me to my last point: You are probably going after the wrong kind of girls. You probably aren't their type dude. Some girls have commitment issues and aren't looking for Long-term relationship material. Some girls want to fix a guy. Some girls are after money, status, fame, etc. Basically, a woman is a bowl; This bowl is pristine, round, and beautifully crafted. It is filled with 10 different kinds of STEAMING PILES OF CRAZY. It's all about finding the flavor of crazy that suits your pallet.
Good luck dude.