Yeah, if you can hit it, then 3d is handy
I'd say the TDU shot looks the most fake, and the composition generally looks worst with regards to different thinks looking 'real' in different ways.
The GT5 shots all feel 'of a piece'... so although in isolation the trees don't look great from a graphical excellence point of view, they 'blend' with the environment really faithfully and don't stand out with their surroundings so much.
I guess it's hard to compare, but watch some real life vs game footage of GT5 circuits, and the trees look really good. You could probably use certain trees as cues for braking points etc. However, SpeedTree types are not used in racing type games so much. They are great for random tree populations, but not so nice for specifics I suppose?!
Making 3D trees en-mass with lots of variation is best left to things like SpeedTree for now I guess. I'd hate to be generating them all manually with LOD's and normal map types etc, with lots of random variation, for a Racer track/road... the only ones I have ever seen done like that are too similar (due to constraints making lots of varieties), to look nice up-close... and often fail to have good LOD to work for a massive amount of trees that you drive past, and also then fail to blend nicely with 'cheap' X-type trees further away.
Tis a tough one for now. I'm lost on what is the ideal solution. SpeedTree is nice because it's all automatic, but to copy that manually in Racer is near impossible, hence everyone who does that kind of thing is using SpeedTree, or if they don't, they use X-types or similar... hmmmm...
All this said, I'm fairly happy right now with x-trees, and good textures, with the new shader Ruud gave us for trees. The ones hanging near the road probably need a few more polygons to break their shapes up a bit, but that is only really to please photomoders' requirements I guess
Hmmmm
Dave