[bit of a ramble]
I think stories about "nice guys finish last" often involves some selfless acts that get ignored or under appreciated (no romantic return on investment) making the guy feel hopeless etc. Selfless acts are romantic and heartfelt once you have established a base level of interest and affection. Your selfless acts have some meaning now that it is not all you have to offer but rather a bonus to who you are, a show of consideration by making an effort amidst the busy-ness of your daily life.
If you open big with "We met yesterday but I quit my job, sold my house and ran a marathon for you why don't you love me" I don't think anyone would put their bets on it. People aren't attracted to overly selfless behaviour as your main personality trait. Know when to step away from being taken advantage of, be courageous enough to say no, put appropriate boundaries to protect your time and emotions, prioritize yourself and all the while be kind and considerate.
Ofc this effect is overbearly obvious and obnoxious with guys who have too much self importance. It is the loudest way to say "I am great" when you are the guy with the ego that fills up a room. This can be enticing at a glance but is unsustainable for yourself and your relationships in life. This is not to say that there arn't people attracted to narcissim or that some people won't swoon over extravagant displays of affection early on, or that your kindness wont sometimes be taken for granted or that you won't be wronged in your love life. Just don't lose your self worth in the mix of it all when you pursue people and put your heart out there. Self respect it is perhaps the strongest indicator of your value.