All I'm hoping for is returning and new tracks combined with improved physics from FM5. While driving in FM4 is still plenty of fun, it doesn't compare to FM5 in terms of how fun the cars are to throw around, where FM4 cuts me some slack and I can recover from careless driving relatively easy, FM5 really keeps me on my toes at all times, you get distracted for a second and you end up in the ditch. I really love this ever-present sense of danger in FM5 which wasn't present in previous forzas.
Now, when I decide to play GT6, it just can't hold my interest for longer than a couple races, I'm instantly reminded of how crap DS3 is compared to X360 pad, let alone Xbone's pad, how crap the sounds are, the framerate slowdowns, the overall feel of the cars that just feel soulless compared to forza. It's hard to explain, but the experience just falls apart the moment I decide to play. It's a beautiful game visually, tons of cars and tracks, but again I have no interest in driving PS2 cars that just become an eyesore on the track and a time drain in the menus. With tracks it's a similar story, yes they're good looking, but what I really hate is how tracks were never changed up during the generation. Eiger in GT6 in 2013 looks exactly as it did in Gran Turismo HD back in 2007. I've seen the track a million times in the last 7 years and I just have zero excitement driving on it now. At the same time T10, even if the track has been in the series forever, they change up the environment and especially the lighting with each version. This manages to keep the content from going stale at least for me, I've driven Laguna Seca a million times in Forza and other games, but I'm fine with driving it in FM5, whereas in GT6 I'm seeing the same stuff I've seen in GT4 a decade ago, same skybox and everything. Just kills my immersion completely.