You know, this discussion about OPs which comes up every few weeks needs some additional layering to make it more interesting. Instead of just comparing OPs, we should actually look at the different types of OPs which are traditionally used, and then highlight which shows in the season apply which types of techniques, and which are more or less successful at using those methods.
For example, the Kuragehime OP which was mentioned is indeed a very good OP, but it is a sort of "story" OP. Whereby the OP itself is a self-contained sequence of scenes which serve to introduce the tone of the series, the characters, while also entertaining by being a mini-event in itself (movie parodies in a dream in this case). Such OPs are generally rare, and only utilized by more ambitious directors or those who want to flex their film making skills to the limit in 90 seconds.
OPs like Fate/Zero and Idolmaster are more traditional "animation" OPs, where the content of the opening sequence is made up of various high quality scenes of various characters and action based sequences which aim to show off the characters doing what they do best, and getting the viewer excited for what the show has to offer. Most often this sort of OP is used for shounen fighting shows and more mainstream mecha anime.
Then there are basically purely visual OPs, which is where most of Shaft's OPs fall under. These are directed like arty music video sequences, which aims mostly to fit visual effects and transitions with the best and tune of the song. Introducing characters and actually representing the show itself is secondary. Several BONES and Gainax OPs also fall under this category (Evangelion TV, RahXephon, Star Driver, Un-Go). Cowboy Bebop and Samurai Champloo also quality.