As one or two here have pointed out, this has nothing to do with complexity. It also has very little do with hardware. Developers now mostly only code for DirectX (unlike the old days when most games were built for OpenGL and Glide also), they don't need to code for specific hardware, that's just bollox - and has not been the case for decades. This myth comes about from some people's misinterpretations of "driver optimisations" - i.e. where a graphics chip manufacturer alters their drivers in some way to detect when a certain game is run and make "on the fly" configuration changes to improve performance for that game - in order to boost benchmark results.
In terms of the whole "complexity" thing, most games consist of a few megabytes binary and several gigabyes of game data (the bulk of which is music and textures). The latter does not need much serious, time consuming, debugging. Also as most game engines simply build upon existing code and add support for newer Directx functionality, there are few "from the ground up" game engines these days. Even the game engines that are advertised as "completely new" - ask yourself: how do you know? Have you seen the source code...?
As to "console ports", it's only the binary which needs porting over - thus the "functionality" bugs, which are the type of bugs which plague most games, will appear regardless of the platform/architecture.
The reality is simple enough - publishers release to targets - these targets have to be hit and if buggy rubbish has to be released then that is what's going to happen rather than miss a release target. Nowadays PC games are mostly bought online, through "content delivery systems" such as steam, which means that bugs can be fixed quickly, post release, by pushing through patches to the users.
This target and profit based business model is why making computer games has turned into an "industry" rather than something a few budding entrepreneurs put together and made a fortune out of it's being exceptionally good. The music industry and the film industry are the same - all have been industrialised, it's not about the music, it's not about the films, it's not about the games, it's simply about the money. It's about getting spoilt twelve year olds and their parents to shell out $$$s for sub standard junk. It's then all about selling DLC to these same people and then repackaging and releasing the same old thing a year or two later.