I can definitely see why some people would be uninterested in GT4. Some people are into driving fast cars down the street slamming into traffic and making sharp turns at ridiculously high speeds. Okay, so not everyone is into that, but GT4 has a lot of aspects that a casual non hardcore racer would comment as "boring". For example, there are little ways to customize the look of your ride, you can only fit it with rims and a spoiler.
Second, there are lots of tuning options that some people would find confusing, with gear ratios to spring stiffness to camber to toe angle, it is easy to not be able to tell what does what (even the text at the bottom of the screen might not sort everything out). And tuning is a very important part of having a sucessful car. You can't just buy a really fast car and jam on all the performance mods, because that normally will make the car handle very bad, thus, lots of crashes, thus, frustration, thus, a negative view of the game.
Third, sense of speed is low. You can hear wind resistance and see scenery fly past you, but you don't get nearly as much feeling about how fast you're going then you would in real life. If you went onto a test track and took a car to 230mph, afterwards you would be speechless and amazed. In GT4 if you do the same, you don't get nearly as excited. "Yep, I'm doing 261 in my Skyline on Le Sarthe. Brakinggg, now going around the corner. I'm bored." You don't feel Lateral Gs, either, but you really can't simulate that feeling with just a DS2, or even a gaming wheel.
About the "fake" comment, I disagree with that being justifiable. You're not going to do like, 200 while making a hairpin turn. Unless this is a really, really, really big hairpin turn. So despite Gran Turismo's physics not being perfectly accurate, there are no games with physics on the market right now that are perfectly accurate. It's far from reality (especially the low speed physics which suck), but arcade-style racers aren't any closer. NOT BY A LONG SHOT. Some of the physics are quite good, but you have to learn how to drive well if you want to be a pro.
So what I'm saying is the game isn't the cream-of-the crop with today's standards, but by no means does it outright suck. It's not a game for everyone, but a racing sim is supposed to be, well, a racing sim. It's a racing fan's game.
Hate me, love me, flame me, +rep me, this is my perspective of the topic.
(Sorry if I spelt anything wrong, little too tired to check it over)