I'm not saying this has been a great Steam sale necessarily, but if I were to count all of the games I already bought on previous Steam sales as "good deals" I probably would have come up with over 20. It's just that most of us have been buying anything remotely decent the past few years so there isn't any backlog at all. There's only so many "good" new games that come out each year, and they can't all get down to $5 right off.
Now, the fact that GMG and Amazon and others are beating them by a little bit is another argument, but as far as quantity...we just have them all already. Someone new to Steam would probably be ecstatic over Bioshock and Mass Effect and Civ, etc. We're just jaded compared to your normal consumer. Not much different than MMO burnout, really. The first time is always better than later attempts, simply because it was new to us the first time around.