Plenty of tiny companies have been able to write games for both XBox Live Arcade and for the Playstation Store. I'm not saying it's easy to get going, but the portion of the difficult attributable to the console is significantly lower than just writing a game.

The real problem with having a separate instruction set and architecture is that it's going to be longer before game engines come out that can be targeted to your system and thus you'll be giving the other guy exclusives that would otherwise have been multi-platform.