First of all you need to get the idea out of your head that there is only one sort of "Facebook Game", and that it is somewhat similar to Farmville. Judging all games on Facebook based on Farmville makes about as much sense as judging all PC games based on the most-played PC game of all times, which is probably Solitaire. There are good and bad Facebook games out there. And then this is "good" and "bad" when viewed with the eyes of a "gamer". A lot of Facebook games which are "bad" to me and you, aren't necessarily "bad" to everybody. I know a woman who is playing a bit of World of Warcraft, but finds WoW very hard. But she rules in Cityville, a game I found far too boring.
Because the target audience for Facebook games is often people who do not otherwise play games, finding a game on Facebook which is "good" for veteran gamers means sorting through a lot of dross. Maybe there is a guide somewhere out there, but I haven't stumbled upon one yet. Most sites discussing Facebook games just list popularity by millions of players. And that strongly favors the least complicated games, which are played by non-gamers in their lunch break. That doesn't necessarily make the "bad" games, but it makes them unsuitable for the likes of you and me. It also creates a vicious cycle for game companies: Zynga recently published a game which was more complicated and more interesting to gamers than their usual fare, and the game promptly tanked.
The second major caveat is Stabs' limitation of "if privacy were not an issue". Privacy *is* an issue on Facebook. Playing most games on Facebook under your real name with your real friends has serious drawbacks, unless your real friends are *all* Facebook games fans. Facebook games produce a lot of spam, clearly "outing" you as a gamer on Facebook. And many Facebook games are "social" in that you need your friends to cooperate to advance. Or pay crazy amounts of money to replace the "free gifts" your friends could send you.
Now for many people this "social" feature of many Facebook games makes Facebook games not worth playing. That is a totally understandable and valid point of view. But as a game analyst, I tend to separate game play and business model. That is basically the same thing as whether a hypothetical PC game costing 1 million dollars to buy a copy of is any good: The game might well be very good, but the cost is unacceptable to most of us. If you have a real name Facebook account on which the friends are your real friends and relatives, you might very well decide to skip a good game because the social cost of having to spam your real friends to advance is unacceptable to you. It sure is unacceptable to me, which is why I got banned for having a false name account and lots of fake friends with which I had a kind of mutual spamming acceptance deal. I basically refused to pay the social cost of Facebook games, and Facebook banned me for it. It might even have been my blog posts about this possibility to avoid the social cost that led Facebook to ban me.
Now Facebook does have some games which aren't using a "spam friends or pay big bucks" business model. And if you have only friends who already know that you are an avid gamer, and your profile has all the privacy settings correctly set to protect you from people you don't want to know about your gaming habit, then you could play Facebook games. Different games have different amounts of social cost, and if you are willing to pay that social cost, there are some good games to be found. Just don't dive in without thinking and end up sending your boss a request to help you click on a cow during work hours.