I've been with a few nice guys and I've really enjoyed the first few months with them before kinda getting bored! The only exception to this is my current boyfriend.
Unless you keep the passion there - the feistyness/a bit of roughness - it can go that way, and I'm sure I'm not the only girl that thinks this way! I'm not saying you have to majorly change who you are, just incorporate a few less "nice" gestures that your girl would appreciate like pushing her on the bed when you're both in the mood for it, or slapping her butt when you walk past her once in a while, you know?
While girls like relationships with nice guys, they also like the thrill of a bad guy at least now and then!
Hope this helped
