Believe me, I'm as tired of criticism as you are (because most threads turned into a circle-jerk of why there's no dlc, PD sucks etc etc and because some people here act like Kaz killed their mother or something) BUT there is no use of pretending that the problems don't exist. And the first step in solving a problem is admitting it exists.
For me personally, GT5 is still great at some things - It's highly inconsistent visually, but under the right circumstances it looks insanely good. The car models (premiums) are incredible and detailed enough to be used in future games. The photomode is the best of any racing game I've seen (just look at the GTPlanet photomode section). Also PD absolutely NAILED the material shaders in this game - glass looks like glass, plastic looks like plastic etc. Some other racing games' shaders look laughable in comparison to GT5. We have online for the first time in the series. The physics need improvement but are still really good. For me those are the positives.
But on the other hand you have the sounds, standard cars, strange and ridiculous game design decisions, Japanese biased car list, duplicates to get to the 1000 car mark, bad AI etc. Some people enjoy GT5 despite those negatives but for some it ruined the game. For me, what bothers me the most is the fact that GT does a bad job at things that were already good in the series. No game in the series has been as plagued by graphical problems as GT5. No game in the series had as slow and clunky menus as GT5. The wheel system (rims) in GT4 was awesome and the best in the series, in GT5 it's really stupid and the worst in the series. Same goes for a lot of things. Then, you have the new stuff like 3D, data logger, head tracking and the course maker which are features mostly good on paper but far too limited to be actual usable features. Museum is cool but wrongly implemented, so most people don't care about it. The level and experience system is a joke, has no place in a simulation game and is here just to make people who like to fill experience bars in RPG games happy. The fact that you lose paint chips when you paint a car is just an unnecessary annoyance.
The standard cars have caused more trouble than just making the game uglier : Because of them the garage is separated, the dealerships are separated and make no sense, photomode is an annoyance on track because of them, etc, etc... And btw, they are literally copy-pasted from GT4 even though PD said they would be updated.
The problem here is not discussing GT's negatives it's the people who want to see the PD staff lose their jobs and insult Kaz personally because they didn't like the game. which is sad. Constructive criticism is welcome, and there are threads here that do exactly that. There is no use pretending everything is perfect. But then again, there are people who were not disappointed in GT5 at all and there is nothing wrong with that. I don't think GT5 is a horrible game, but I do think it doesn't have the quality standard of a GT game. And that is why most people would consider it the worst in the series.
