As I see it at the moment even the consoles are now basically pc based with basically the same gpu systems.
The best way Amiga could make a comeback to start would be as a brand new high performance deskstop os, that works better than windows , linux or mac osx.
If it was good enough and built the right way it could work, look at the mess Windows 8 is in, never been a better time while windows is looking so weak, and company's like valve are developing SteamOS.
Trying to better intel CPU technology and Nvidia or AMD for graphics chips in the desktop arena isnt really viable they are the top of the food chain in the desktop arena.
The biggest issue is gaining developer support for software or apps as everyone now calls them, look at blackberry they now have no unique selling point anymore and are trying to compete with Apple and Android stores with millions of quality apps already available.
As said before many good consoles spec wise have died prematurely due to bad software support look at the dreamcast or saturn/playstation battle.
If you can revive amiga as a breakthrough OS then anything after that is possible, you would need some killer app or game though to make people move.
I for one kept my A1200 longer than all my friends hoping that commodore would sort itself out had an accelerator cd rom hard drive etc but in the end software dried up, no new hardware and seeing games like doom, and then tomb raider and Jedi Knight running on the first 3D cards made me want a PC.
The same thing when I first viewed shadow of the beast, made me want an amiga, got to have a killer app.