This is an interesting topic. I think you are right that generally the first OP of a show is the best (putting your best ideas out front and all), but there are some exceptions. I can think of Nichijou and Hyouka, for instance - Nichijou's second OP meshes better with the music than the first while Hyouka's has a better concept. Can anyone else think of other shows where the second OP is better than the first? (Obviously in long-running shows such as Naruto and Gintama with tons of OPs, it's pretty easy to get a better OP than the first somewhere along the line.)
Jojo