Right, there is a very fine line between success and failure in this area.
To answer your question bluntly, yes, I think it's essential.
However, where many people, myself included, go wrong, or in my case have gone wrong, is confusing making a girl feel special with just being overly "nice."
For example, if a girl you're with mentions that she really likes the look of a dress or something, not asking for it but just mentioning it, then say a few months later it's her birthday, if you remember that exact item and buy it, then it shows you listen, you care about her etc, you're not like every other idiot that ignores everything she says and buys her chocolate and flowers etc. That is good. As is rewarding her for stuff, say she got a job promotion, cooking her her favourite meal (and more to the point knowing what her favourite meal is) is never ever a bad thing.
But people over do it. Women should feel special when it's deserved. If she's been a ***** lately then she should be treated as such, not showered with attention etc to try and bring her out of it. Unless you have done something seriously bad to provoke said *****iness, which is usually not the case, then you should do nothing to bring her out of it. Doing so will make her realise you're scared of losing her, etc etc, which then destroys the whole "challenge" aspect of a woman's mind, which then often spells game over. There are a few mistakes I made with my ex along such lines, I can see them for what they are now.
Basically, you make a girl feel special by showing her she's lucky to have such a brilliant boyfriend. You make her special by showing you listen, actually treat her as a human being not an object and actually see a difference between her and every other girl. That is not being AFC, that is being above and beyond what most men are capable of. But if she doesn't deserve that kind of treatment then she should not get it. The problem most people make is deciding when that treatment is or isn't deserved, because most girls will expect it 24/7, even though if you give it to them 24/7 you end up on the wrong end of a "we need to talk" style text message.