I fear I'm gonna be bashed here, but this is my story (and rant):
1. having convinced the mrs. that the PS2 was good for our children to play games, and also a not too expensive DVD player (so we could see some movies), I finally bought my PS2, I think it was in early 2002. And I bought it together with GT3 and the Logitech DF.
2. until GT4 was released I played intensively GT3, than GTC, than GT4
3. The only other racing game that made me stop playing PD's games for a while was 24H Le Mans. And I played that game always hoping that GT4, when released, would also have endurance races, dynamic weather, day/night cycles, at least 20 cars on track (LM has it, and it's a 2000 game).
4. GT4 became available at the local store where I usually buy games, by midnight of a particular day (can't remember exactly the date). I was there since 11h30, and even pre-ordered the game just in case. Left the store, with the game in my hand, at about 1:00 am, and I played it that night up until 4:00 am.
5. It was overall a better game than GT3, but the feeling I increasingly got from it was that it was "more of the same". More cars, more tracks, more races, and more graphic detail (even if less than the "litle", but very enjoyable, GT4

).
6. Anyway, it was my new toy, and I played it intensively, night after night after night, until I started to get a growing feeling of boredom ... at about 85% of game completion (everything made except the enduros. Can't stand 24 hours straight in A-Spec, can't keep the kids away from the PS2 for several days and I refuse to use the stupid B-Spec thing. That's not even a poor team-manager sim, it's just a way to make us forget that they didn't want or didn't know how to allow midrace saves ... ).
7. And this - the feeling of boredom - never happened with GT3, a game I played many times in three years, restarting from scratch, GT mode after GT mode.
8. In May, Enthusia was released, and I also bought it (didn't pre-order, didn't leave the house at night to buy it, it was just a question of "hmmm, let's see how it is ...")
9. At first this game wasn't glamorous. The dark menus seem outdated, the game structure is confusing, and the immediate comparison with GT4 is: a) less cars; b) less tracks; c) less races; d) dark nurburgring; e) undriveable cars.
10. However, I kept (still keep) playing and replaying it, alwasy finding new chalenges, interstingenough to get me going. I won't go in detail about it here (you guys have a Enthusia forum in these boards so here it would be out of place to do it).
11. And ... I never even touched GT4 again. For almost a year now.
12. Why? Well, I think because GT4 has no re-playability value. And because the races there seem ... fake. The AI opponents are laughable, and when they aren't it is because there's ONE car in the lineup that blows the competition ... except you (maybe).
13. I won't say anything about the physics, there are members of these boards that have incredible knowledge about that (I remember particularly Scaff - that thinks overall GT4 is the winner - and Wolfe 2x7 - that thinks the same about Enthusia), so I will just say that the GT4 physics engine didn't impress me.
14. I have always been, and still am - even if, by now, people who had the patience of reading this rant think otherwise - a PD fan. I still think those guys have, with the GT series, really pushed the console racing games to a level difficult to imagine a few years ago.
15. But I think GT4 fell short of the heritage of its predecessors. I regard it as a false step, probably dued to the impossibility of delaying once again its release.
16. Until I have the PS3 and GT5 at home (and I plan to buy them both as soon as GT5 is released, unless other racing sim for the PS3 is released earlier), I don't think I'll pick GT4 from the shelf very often. If ever.