Ideal ctr=0% and ideal ecpm=100000000000000000000000000$. However it better to keep ctr less than 20%
There is no ideal except to have both values as high as possible. There seems to be some mistaken notion that high CTR is not good. The only time high CTR is bad is when it comes from invalid clicks. High CTRs are very common on sites that make serious money with Adsense. In fact, it's the very reason those sites are successful, even without tremendous amounts of traffic.