@ c0rd
When people argue about the 360 and PS3, it's ridiculous because it practically takes experts to determine which system is better than the other. If it has come to that, the graphical difference simply doesn't matter, even to most of the people on this site - if they say otherwise I'd guess it's out of console fanboyism.
Although I agree with regard to the endless threads created by 360 fans about the minor early difference with regard to 360 to PS3 conversions. IMO the long term differences are pretty big, Blu-Ray, default harddrive as well as the Cell processor make quite a difference with regard to long term potential.
Of course with the 360's headstart and the PS3 being very differently architectured than legacy systems in some crucial areas (requiring game engine redesign and imposes a small learning curve) the already demonstrated differences in current games are smaller than will be the case for the long run. (Hurdles I already talked about years before the PS3 hit the market)
And I agree with you about any kind of game can be done on any current generation console, but with sacrifices, not only graphics (anti-aliasing, resolution, polygons, texture quality, etc) but also with regard to things possible to do on screen at once and at what performance, complex AI, world size, world complexity, physics, sound quality/complexity, etc, etc.
Of course like Squilliam pointed out, the more resources available and more features implemented, this usually leads to far more complexity. For instance the Amiga provided custom chips which were extremely powerful for their time and provided pre-emptive multi-tasking, although it was often still possible to take simplified approaches within a couple of years game engines and programs became a lot more complex compared to similar less impressive versions written for single tasking systems lacking such advanced custom chips (competitively push games and programs ahead of rival offerings).