The phony nice people are hard to spot. They put on such a good face for so much of their lives that they almost convince themselves they are nice. But the difference is that the phonies have ulterior motives. They aren't nice for niceness's sake--they're nice because they want the promotion or they want you to scratch their back someday when the karma comes around, or some other less than entirely altruistic reason. These people can sometimes be even worse than mean people because they may be manipulating you without you even knowing it.
The real nice people, we know who they are, will do everything because they want to. Because they care. They'll always offer you a soda if they're getting one for themselves. They'll always hold the door. They always say "Gesundheit" or "bless you" when you sneeze. They worry for your soul escaping from your body when you have an allergy cold and can't stop sneezing. That's true compassion. They may get put down and laughed at, taken advantage of and overwhelmed, but they will keep doing what they're doing because they can't imagine saying no or making a misstep in their manners and overall kind and generous demeanor.
We also have the people who hate themselves for being so nice. They wish they could be mean. They wish they could exhibit some level of dominance and say no once in a while. These people worry too much about what others think. They know people think they're too yielding. They know people call them a doormat. But they can't help being nice. If you are a truly nice person, you should accept it, embrace it, and learn that most people appreciate someone who cares more than someone who can assert some authority.
But are the nice people too nice? I can't stand morning people. Morning people are usually nice people. They're too cheerful at an hour that seems impossible to me to be cheerful during. Nice people tend to make me feel bad that I'm not that nice. But I don't care about the same things. I want to get along with people and I want people to like and appreciate me, but I'm not going to say "bless you" when you sneeze because that's one of those mannerisms or superstitions I never bought into. It's a sneeze, a few moments in your chest and out your nose and mouth. It's not your soul trying to escape. (The origin of saying bless you is because people used to--or still do, apparently--think your soul would escape when you sneezed if someone didn't bless you.) Sante or salud might make more sense--to your health, because yes, you're sick, that's why you're sneezing. But I digress, as usual.
Even if morning people make me cringe a little bit sometimes, I'd still rather be around people that are too nice, genuinely or not, than people who suck. Clearly, I'm a little over-tired, and I probably rambled on a bit about something that mean not mean a whole lot in the grand scheme of things, but self-deprecation is not an attractive quality either, so I'll knock it off. Being nice is good karma, whether you believe in karma or not, and it's always preferable to being an asshole.
Just be yourself. Odds are, someone will like you in spite of it.