Yes, "true fans" "fanatics" however you want to put it can be and often are satisfied. It doesn't seem that way because satisfaction is the "end" of the cycle. I see this in my work all the time. This is the scenario; you put out a product that 100 people buy. 99 are completely satisfied with the product, and 1 is not. The question is "who do you hear back from?"
In a sample like that, you will only hear again from the dissatisfied customer. Industry studies (in my industry) find that for every 1 person who calls us with negative feedback there are anywhere from 100 to 1000 people who are satisfied with the exact same product. We're told to be positive about those negative calls because the more of them we receive, the larger our audience must be.
Now on forums and such the difference won't usually be as stark, but I do believe that for every posted naysayer there are at least 2 folks not commenting who are totally happy about the product. Videogame, tv show, or what have you. Looking at the forums over on IMDB one would get the impression that the NBC show "Revolution" was a steaming pile that people only watched to have something to ***** about. But are they right? No, E! just ranked it as one of this year's breakout successes. What you see in online forum negativity isn't rational criticism (for the most part.) It's people who couldn't keep a check on their expectations, people who have a persecution complex, juveniles who don't know any better (and that's not a shot at age, some young folk learn early and some old folk don't learn at all,) prima donnas, and people with low self esteem looking to fit in with the crowd of all of the above because they are the only ones participating.
And it gets worse over highly anticipated material. Using novels as an example; George RR Martin took 6 or 7 years to write his last 2 novels. By the time they came out expectations were huge. And which of his books were the most complained about and the least well received? The last two, and that's no coincidence and it has little to do with the overall quality of the product. But again for every person online whining about how "the series has gone downhill" two others go online and see all the vitriol and just don't bother getting involved. They just shut the book and find something to do while waiting for the next.
Or to use one last scenario, think back to all of the "customer survey" print outs on a receipt you've gotten. How many do you actually fill out? And one last question, are you more likely to fill one out if you are pleased with or dissatisfied with the service somehow? Most (and I'm no exception) may fill it out if we are happy with the service, but will almost always fill it out if something went wrong. It all goes back to "satisfaction is the end of the cycle" so yes fans can be and are more often than not pleased. If all the negativity depresses you (it does me sometimes) just remember that there are almost always more positive people than all of the negative shouters... you just don't hear them.