For the most part the last Amigas sold were not even that different from the first ones (AGA being just a little tweek of OCS/ECS). The original Amiga games from 1987 sucked, it took a while to figure out how to program the graphics to make use of the Amigas power (and generally you needed 1MB of RAM for most of the good ones something most A1000 owners never had). A standard IBM XT would not even have 640K RAM don't forget, My Tandy 1000HX came stock with 256k of RAM, which I upgraded to 640K.
VGA cannot do CGA colors well , which is why I have a nice CGA monitor for my Tandy. People showing CGA games on VGA are just making a system look bad on purpose.