As developers in general, they are fantastic. Skyrim is one of my favourite games of the generation, and I loved Oblivion and Fallout 3 as well (New Vegas not so much, but that's just a personal thing).
But, we are in Sony Discussion. So, yes, there is little excuse for the shoddy job they do on the majority of their PS3 games. It's true that the PC and Xbox 360 have similar and basic architectures, but we are now six years into the lifespan of the PS3; it's above 60 million units, which is a userbase that only a fool would ignore; plenty of games, both first and third party, have taken great advantage of the PS3's power, and made games that look great and run well.
At the end of the day, it's their decision how they want to spend their development resources. They don't have as much of a fanbase on PS3 (largely because they shaft it so much) and as such they see no reason to "waste" disproportionate amounts of money on it.
(Former) Lead Moderator and (Eternal) VGC Detective 
