In my honest opinion, GT5 is more dead than GT2, mainly because you now absolutely must have all the DLC to have just a tiny bit of fun online, which is the only fun part as the AI seems to have drawn it's license in a candy dispencer. B-Spec is good in the theory but making B-Spec events 2x longer than A-Spec is a big no-no. And you can't really use them for anything. And the cars. The lovely cars that are divided Premium/Standard. I wouldn't give a f-word had all cars had a reasonable cockpit and a fair bit of details, say around 50.000-100.000 polygons (Kaz said GT4 cars were 5.000 polygons IIRC and GT5 Premium are 500.000(!!)) and if there wasn't 50 Mazdas and Civics that were identical bar the regional name. Ferrari and Lamborghini coming to the series were good but we've dealt without them before. And most of the cars in GT5 can be driven in any other game. To compare to GT2, had we heard of RUF, Vector, Venturi, Tommikaria etc. if they weren't in GT2? No, because they were nowhere else to be found. What GT is missing is more equal-in-detail cars, more special/GT only cars, and the ability to not have to release DLC to keep the game alive. DLC basically does nothing but making a game feel less complete because then people start making even higher requests.
Rage over