Well, the Amiga was a success because it was different and was offering great multimedia capabilities when everything else was inferior (only the ST was close and is no coincidence that both machines dies simultaneously).
For the Amiga to be a success today, it had to be different. Computer hardware today is evolutionary. Amiga's hardware back then was revolutionary. I don't see how the Amiga's hardware today could have been revolutionary.
Same can be applied for the OS. Back then AmigaOS was exceptionally good and was unique. Today, we have so many OSs that are great. Of course, I am not talking for Linux, Windows but for OSs like QNX and MacOSX. So, Amiga had to offer a unique OS again but I find this a bit 'not-easy'.
Considering prices, Amiga's custom hardware means R&D, higher production costs and generally, expensive hardware. If Amiga had to be cheap and powerful (I am not speaking just for the CPU), they had to follow the mainstream route. Therefore, to keep costs low, they had to be mainstream.
I am not sure if Amiga would have been different to an ordinary PC and if it was going to be, it would have been V. expensive.