One thing for certain is that this gen would have been radically different. A $400 ps3 with blu ray released 1 year earlier would have been siginificantly weaker than the 360, considering how expencive blu-ray tech was in 2006, let alone the year prior.
The 360 would end up being the only console able to run hd games.
Most third party games would have been made subhd to be ported between all three consoles, which could have made the wii much more successful.
360 exclusives would have looked ridiculously better than anything on the ps3, especially later on, which would have helped the 360.
Playstation obviously starting at a reasonable price would have greatly helped its initial sales, but not being able to have the better looking "hardcore exclusives" could have hurt it later on.
I think the ps3 would not still be selling well had it gone the underpowered route. Whether it would have made up the difference with more initial sales is hard to guess.
