Do nice guys always have to finish last?

Is the old adage, 'Nice guys finish last' really true? Unfortunately, I've seen too many instances to prove the theory, so I'm going to say Yes....with exclusions.
I think that nice people are the coolest. I am a positive person by nature, even when sometimes it's hard to force myself to be positive. Does it really hurt to be happy? Why do people want to be grumpy? You can usually tell the difference between optimistic people and pessimistic people. Or as my husband calls them, 'realists'. (Guess you can tell which bucket he falls into, hmm?)
As an optimistic person, sometimes I feel like I have to explain my happy attitude, or at times be embarassed of it. But why is that? Do people think that nice people aren't REAL people? Like they are artificial or fake? Are we all supposed to be curmudgeonly? (It's really a word...'An ill-tempered person full of resentment and stubborn notions'. You're welcome.)
In the past few days, I have three nice friends who have experienced a form of curmudgeonliness (ok, not sure if THAT is a word, but bear with me and stop nitpicking). One posted a story on Facebook that dealt with the 'Nice Guy' syndrome, and felt like she had to explain why she herself was a positive person. Apparently some people thought it was fake, that noone could actually be that nice. But she tried to stress, 'Look people, it's REAL.' Why do we have to do that? Like nice is a bad thing?
Another friend is always being overlooked....whether it's in his job, or with the people he hangs around, he seems to be invisible. I've experienced this myself, and it's pretty damn humbling to meet someone, and then a week later they have forgotten that they ever met you. Ouch. In his case, his 'friend' forgot that he had ever been to his house. But he had been. Three times. 
And yet another friend suffers from the Extremely Nice Guy (gal) Syndrome. She puts everyone else first, and contents herself with the leftovers. She doesn't have a thought for herself, and unfortunately there are people out there who take advantage of that. Recently this kind, gentle lady suffered from the thoughtlessness of another, and that's perhaps what hurts most of all...to give yourself so fully, and to have it be insignificant to someone else.
What is wrong with being nice???
Nothing - that's what. But the nice, happy, optimistic people don't go trumpeting ourselves, which is perhaps why we are the most misunderstood. Because it's not in our nature to put our good deeds on blast. We hear about thoughtless, heartless, hurtful deeds all the time -- media sensationalizes it -- and so we think that's all there is.
But it's NOT.
Let's celebrate the nice people, shall we? Secretly, quietly....we make the world go 'round.