Ok, diversity is the wrong word perhaps, but T10 clearly concentrate on cars that they know car nuts around the world want in a racing game, and no duplicates! If only PD could get rid of duplicates it would instantly make the game better in my opinion.
Strittan, I truly get where you're coming from, but I gotta add something of myself here. You see, I like GT6's carlist, a lot. I am truly happy that they finally added some premium Diablo's, of which I guess the whole forum knows that it's my favourite car ever (in every iteration and model make), because to me it represents both the true, raw, uncompromising spirit that seperate(d)s Lamborghini from the likes of Ferarri, and it represents the moment I fell in love with racing games (Need For Speed III: Hot Pursuit, which I think needs no introduction here). I have never whined about it not being included, and truth be told the cars got so old I highly doubted they would've ever made into the GT games. Alas, waddya know, they're here, including that ungodly GT2 version. No, it's not the version I love the most (the SV obviously), but I love it, truly, truly love it. But that gets me to my point. You see, the Diablo (and a whole bunch of other cars I love to drive) aren't or weren't represented in GT ever. The likes of LaFerarri, all Porsches (Ruf can't make up for that devilish 959, sorry Ruf lovers...) and a host of other man-made monsters come to mind. Yet Forza does.
On the other hand GT has had a whole bunch of cars I never knew and were big, big surprises to me in the past and still in the present. I guess everyone here remembers the insane Renault Espace F1, the Suzuki Escudo (**UNASHAMED NOSTALGIA ALERT** the car was literally unbeatable in GT2, was my main moneymaker and I still long for the days of driving Red Rock Valley over and over again for what I believe was a TVR Speed 12 that could be sold for a hefty buck), the Chapparal's, Toyota GT1, and many more.
My point? I play both games. I love both. There, I said it. I love both equally even though I would find myself in the hate-Forza-for-no-reason camp in the beginning when I hadn't even played them. How wrong I was, afterwards. Both have flaws, both are not perfect. Heck, I even still play Shift 2 from time to time. I love all games for what they are, yet I have a special place for GT that I truly feel I shouldn't have to defend, because it's a personal emotion I have with the game. One does not need the cars from the other. THAT my friend is the very reason both can exist in the same time, alongside each other. Because they are different. I love the addition of the Lunar Rover. Smiled when it got announced because it would be something only GT does. And I love it for that, for it's quirkiness. For some more siriuz bizznizz, I play Forza. For the feel of driving automotive history scattered across an insane range of cars, I play GT. For audiovisual pizzaz, I play Shift (for those people talking about visual customization, play that game and tell me you kept your pants dry while seeing your Porsche 911 GT3 grow from street car to absolute racing monster including cockpit upgrades). For relaxed driving and poking around, I fire up the original Test Drive Unlimited and even Driver San Francisco (talking about insane car lists!).
What I don't find in one game, I get in another. I love it that way, to be able to get different experiences from time to time. That is, for me, the true definition of a racing game enthusiast (mind I said racing GAME not SIM), or a gamer as a whole, the ability to love or hate something for what it is. It's the discovery, not the result, that yields the best results. Therefore, I would never say GT should include some cars over others, nor would I do the same for Forza or any other game.
This concludes my little speech. God I should have had the American Flag on the background whilst playing the National Anthem while typing this!