My two kopeks.
You included the 1911. I'd add: a Browning Hi-Power 9mm; a full size "wondernine" by Ruger, S&W, Beretta or CZ; a Glock or at least an iteration of the "modern wonder-whatever" (i.e., high cap polymer pistol); and a good target auto, either a Ruger Mark, High Standard or S&W 41. Additionally, in a collection, I'd want to include an example of the "small self-shucker." I remember when the SIG 225 was considered a tiny 9mm. Ha! Those were the days. I don't know if I'd go polymer or steel for the bitsy 9mm, but I'd definitely consider something like a Rohrbaugh, Kahr MK9, or Kel-Tec.
Those are my thoughts on what would go into a "general semi-auto collection." I was focused on a sample of major handgun trends, without any brand loyalty or deep thought towards tacticimal applimications.
It just occurred to me that if I was putting one together like that, I'd get a 5" 1911 in .45 ACP, a 9mm Browning Hi-Power, a CZ75 9mm, a Glock 17 9mm, to show the evolutionary process in "big service handguns." Perhaps, similarly, I would do the same with "little carry handguns" and put on a Colt 1903, a SIG 225, a Kahr K9 9mm (preferably a "flatside" model predating the adoption of the .40 frame) and lastly maybe a Rohrbaugh.
Oh my, this could get expensive.