I think when people are looking back on the Gran Turismo series, when they think of GT 6 they'll first remember how PD was able to really stretch the resources of the Playstation 3. i never played GT 5 but I've heard a lot about it here in the forums. A lot of people talk about GT 6 like its really GT 5.5...maybe that's fair, maybe it's not I don't know. Just the other day I sent my brother a couple of photos taken from my phone (I had rolled my Nissan GT-R on Nordschleife) and his comment was "Wow...Your game really does have nice graphics!" He owns an XBox One and Forza 5, so I took that as a very nice compliment.
The number of cars, including some terrible Standard models and some decent Standard models is incredibly impressive. There literally is something for everyone. Along with the very impressive number of tracks, GT 6 can't be accused of shortchanging it's customers in those two regards. Personally, I'm a little ticked off at how long certain features took and the fact that course maker w/gps never came (it literally was one of the features that made me buy the game), but I have been blown away by the realism of just driving a car. GT6 has opened up a whole new world to me. I have a new laptop being assembled as we speak and I look forward to trying Assetto Corsa very soon (and probably PCars at some point). I have Gran Turismo to thank for introducing me to this virtual world of driving/racing.