I have a sharp 18 x 12 print here from a Sigma 12-24 at f8 and that's totally smoked by the 17-40...
You are unrealistic in your expectations.
Sure you can get sharp wide angle optics, but they are fixed focal lengths and are expensive (even the famed Nikon 14-24 has issues). Do you really think lens manufacturers have high prices because they're making obscene profits? No, it's because they are difficult lenses to design and manufacture....
Nikon 14-24 issues are pretty minor; flare mostly due to bulbous design and no easy way to use filters. This can be significant to some, but many canon shooters have adapted one in despair
Canon sadly now focuses more on video rather than their core wide still lenses.
TSEs are great if you are willing to accept MF and no filters on 17 as well as the price. This is a seriously interesting option
20mm f/2.8 badly out of date and very poor. 17-40 performs better (!) and so does 20+ year old nikon prime. Shame!
17-40 - I've said it all already. It was fine in 2003, now it's almost 2013 and sensor technology has moved on. It doesn't compare against the ones like 70-200 II or even the old 24-70mm at 24-40 range.
24mm 1.4 II - not that wide, and arguably 24-70 is good enough anyway, but it's OK for a change.
16-35 II - supposedly better than 17-40 but nothing stunning for sure. Nikon 16-35 f/4 outperforms it at same apertures at lower cost. :thumbsdown:
now let's take tokina 12-24mm for example. It will work on FF fine from 18mm and is pretty sharp even in the edges. The only complaint is lower contrast, flare and there is some very mild vignetting all over the frame (same on crop). Price - £250 used - not a bad for sharp 18-24mm f/4 zoom. 17-40mm just doesn't compare against this one in terms of sharpness wide open.
so how are my expectations too high?