The 28/2.8 Canon FD SC is an excellent lens. The 28/2.8 New FD whoch replaced it does not seem as good. The 28/2 FD SSC is an excellent lens. I have never compared it to the 28/2 New FD. My only Canon 24 is a chrome front FD SSC. Once its rear element separation was repaired it worked very well. Most people who have used the 24/2 and 24/1.4 lenses seem to think the f/2 model is better. The 35/2 FD SSC (1st version) and 35/2 New FD are both excellent. The SSC lens may need the UV treatment to clear the color. It is also beter made. There was a 35/2 FD SSC with a convex front element (2nd version) which has no color problem but which does not have the reputation of the earlier FD SSC. I saw one of these last Sunday. To go wider than 24 with Canon mount I have the 19/3.8 Vivitar, 20/3.8 Vivitar (M42 with an adapter) and 21/3.8 Vivitar T4. The 19 needs to be closed down a little. The 20 and 21 are both good performers. I have a 17/3.5 Vivitar for Konica and a 17/3.5 Tokina RMC for Minolta. Both are good.
I bought a Vivitar 19mm f3.5 FD fitting lens new as a stop gap until I could find a Canon 20mm f2.8 in good condition, and although the Vivitar isn't terrible the Canon one is much better.