This thread may have been better-placed in the Canon Corral forum: maybe a
moderator should move it there?
* Can. EF 50 1.4
80mm-equivalent on a 20D (more a portrait-telephoto length than a standard lens).
A nice lens with FTM (full-time-manual) focussing. USM focus is silent and fast too.
Approx AU$630
* Can. EF 50 1.8
80mm-equivalent.
A cheap lens with excellent quality but a noisy focus motor. I have the old Mk.I version of this lens (still available on eBay).
Approx AU$160
* Can. EF 35 1.4
56mm-equivalent (close to a standard lens).
A beautiful lens (it's one of Canon's "L"
models) with USM and FTM.
If cost is no problem this is the one I would recommend as a general-purpose lens out of this lot.
AU$1500+
* Can. EF 35 2.0
56mm-equivalent.
Basically the same focus motor/etc as the Mk.I 50mm/1.8 (they came out at the same time). Not a bad lens (can't comment too much as I haven't used it - I expect the quality will be good).
Approx AU$550
Of course that's just from the list you provided. There are lots of other fine lenses also (including some made by Stigma). Keep in mind that the theoretically-standard focal length for 35mm cameras is 43mm (for a 20D that's 27mm). So you might want to look at the 28mm options also...