In a sense it's more like saying that what was originally designed to be an electric milk float should have been an electric milk float. That's also not an entirely fair because I agree that the Amiga makes more sense as a computer. As a game machine it was soon beaten by more specialized hardware that did exactly what action games at the time demanded really well and nothing else.
An exception that proves the rule, in the sense that they were all largely unsuccessful.
Successful video game systems like the NES, PC Engine, Master System, Megadrive and SNES were all designed around tile- and sprite based video generation, like successful arcade games. Similarity to arcade game systems (and arcade ports) probably made them more attractive to consumers and thus more attractive to publishers and developers.
Porting attractive arcade titles to the Amiga must have been an absolute pain because the Amiga doesn't particularly address their fundamental graphics model. You do everything with the blitter and copper and have to come up with clever ways to move lots of layers of tiles and characters around. What's trivial work on a system built these types of games (upload graphics and tile maps to VRAM, move sprites about and scroll tile layers by writing to a couple of position registers) becomes a puzzle on the Amiga.
I also think that the best Amiga games were better suited for computers, like point and click adventures or strategy games like Civilization. The arcade ports I can think of in particular are mostly of poor quality with some exceptions, so evidently it was hard to on-board people who could develop quality arcade ports for the system. The games that really pushed the system technically and that people tend to remember fondly were almost all released at least half a decade after 1985.
But what I meant - what if there could have been arcade games based on the Amiga, so you would not have to port it to Amiga, but it would have already have been Amiga?
And games console with Amiga hardware but say, 256kbyte RAM and 32kbyte ROM cartridges would still have been an awesome games console. All games for that hardware would have been trivially ported (and possibly updated with more graphics and sounds) for the computer Amiga.