One thing to keep in mind (particularly when you're talking about old games for machines like the Amiga) is that often there were factors other than the capability of the machine or the language that affected the limitations placed on games. When the majority of Amigas that had been sold were older machines that didn't have AGA, there was little incentive for a game developer to create games that required AGA features, since that would limit their sales to only a small portion of the Amiga market. On the other hand, if they avoided using any of the expanded AGA features, they could sell the game to anybody who owned an Amiga, regardless of the model. Developers usually catered to the lowest common denominator in this way because it made good business sense. With today's PC's, you don't really see this sort of thing anymore because the size of the potential market is immense, and the majority of machines out there have specs above what is required for most software to run.
As for the languages that were most often used on older machines to produce games, that would partially be just a matter of preference for the developers, but not always. For a turn-based RTS game, the language used might not make much difference in performance depending on the complexity of the game. For an arcade game like Shadow of the Beast though, the language selection could be critical. Where performance was a real issue, most programming was done using assembly, though I'm sure there were some exceptions.