Hehe... the guy who said "GT5's suspension modeling was already in advance of anything short of Assetto Corsa" asks me if I'm joking...
If you're judging the quality of a physics engine by how much the suspension moves, you're doing it wrong. When you say 'it barely moves at all', I'm not sure if you're criticising the amount of suspension travel, or the rate at which it animates - either way there are explanations. There isn't a large amount of travel in GTR2 because they are all GT1/NGT cars - they are very stiffly sprung with very little travel. If you're watching the movement and thinking it there should be more reaction to bumps in replays - this is because the replay fidelity in that engine is much lower than what is actually being calculated in the simulation - this is well documented.
There is nothing wrong with the suspension model in GTR2 - it is based on ISI's engine, the same engine that has been used in many successful sims. Indeed, it is the same engine that is still being used by Reiza, who just launched Game Stock Car 2013, widely considered to be one the most accurate sims on the market. And it is the exact game selected for the Power and Glory mod, another highly-praised sim led by Aris (Assetto Corsa physics guy), who was still working on the project in his spare time earlier this year.
It's clear that the base physics engine alone is worthy of comparison to more modern titles - and when you start to consider the additions like live-track evolution, marbles, that Simbin added themselves... well it's fair to say that GTR2 is not a joke.
Ok you have repeated that childish remark twice now so please back it up. Show me a PC sim with a suspension model better than GT5 that is out now? You can find better tyre models, better 'push arbitrary button to start engine' models but as for the suspension and the weight transfer of the cars most PC sims are crap.
And saying that the GTR2 engine runs in many games proves only your ignorance of the way physics models are programmed. Almost all sims run the same basic equations needing the same basic fixes. You could use just about any sim engine and make it arcade or sim depending on how you configure the variables and interrupt the equations. And the fact you mention peripheral things like marbles suggests to me that you are yet another who judges a sim not by the driving model but by what surrounds it. They have nothing to do with the physics of the suspension nor calculating the dynamics of the car on the track. But they are very useful for making people think wow, this arcade racer is so realistic...