For starters don't flame or troll anybody. I know these topics get heated sometimes so please guys keep it respectful. I just want to see what the predictions and reasons people have.  When all said is done I want to see who is and isn't correct when we get metacritic scores.  

Last 5 Games from Polyphony Digital

Gran Turismo 5(2010) - 84 
Gran Turismo PSP(2009) - 74
Gran Turismo 5 Prologue(2008) - 80
Gran Turismo HD Concept(2006) - 82
Gran Turismo 4(2005) - 89

Last 5 Games from Turn 10

Forza Horizon(2012) - 85
Forza 4(2011) - 91
Forza 3(2009) - 92
Forza 2(2007) - 90
Forza Motorsports(2005) - 92

I think forza 5... generally because critics will have less of a hard time giving GT6 low scores, Because they already have given a mainline GT lower scores.

I liked forza 4 more than GT5 at release (I haven't played GT5's bazillion patches/updates). Also Forza 5 gets a release on a newer console and this is the one I'd expect to get higher ofcourse.

Yeah they have had a lot of patches huh?  Been a long time since Ive played GT5 but good thing they supported it for the last few years to improve it.

Forza will win for a couple of reasons.

Next gen bonus.

Arcadey racing is generally more fun than Sim racing.

I don't know about Forza yet but I think it will receive a score below the 4 and 3.

GT6 I already did my prediction... I will stay with it.

92-94 http://gamrconnect.vgchartz.com/thread.php?id=160350

So GT6 will have the higher score.

Gran Turismo will score lower because it's on current gen systems and people (for whatever reasons) will compare next gen racers to GT6.

Why would Gran Turismo 6 score any differently than Gran Turismo 5? What was wrong with GT5 that won't be the same in GT6?

Forza Horizon wasn't developed by Turn 10, so you might want to remove it from the list.

Since Forza 5 will be on a new console whereas GT6 will be on an old console, I think Forza 5 will score better.

It was developed by both Turn 10 and Playground games as far as I am aware.