I know that, as a driving simulation, GT5 is outstanding, but that's all it has...
There is no damage model. Well a handful of cars can be wrecked visually but that's it.
AI is piss-poor.
The exponential XP system is massively flawed.
The in-game economy is nonsense.
The only genuine challenge is the Vettel challenge, which is just
astronomically difficult.
Licenses are meaningless.
There are less than a quarter of the A-spec races in comparison to GT4 (127 instead of 522) and most of them are hilariously/embarrassingly short. In the German Touring Car 'Championship' for example (a couple of single, very brief races) we got ONE LAP of Nurburgring!
A vast majority [around three quarters] of the cars are ported from GT4, and look awful, with no cockpit view. PD are actually so embarrassed by the quality of these models that when you get close with a camera we are told to 'move further away' (so we can't get a close look at just how awful they are).
B-spec is hopeless, yet twice as long.
Tsukuba endurances.
Countless Skylines and MX-5s.