Looking at the tyres in GT5 the comfort tyres seem to be your everyday 'street' tyres, the sports look like semi slicks and the racing are obviously full racing slicks.
Most real life cars would come with comfort tyres with higher end sports cars (Ferrari/Lamborghini etc.) using comfort softs.
There are a few manufacturers that equip some models with semi slicks from the factory, though this is fairly rare.
Hope that helps. :-)