I really 'love" to read discussions such as "FSX supports 4096 hi-res textures and FS2004 doesn't"...OK, cool...so what is the freaking point to have these 4096 textures if I must to resize them into 1096 to get rid off OOMs.
As usual, it depends what you do with a feature.
We used 4096x4096 textures for KLAX, not to get extra eye-candy, but to get more SPEED. We are consuming exactly the same amount of video memory as before but, instead of having 80-90 textures for the ground+buildings, we have only 6-7, and this is a big increase in efficiency, since each time the video card has to switch to a different texture or material, there's an impact.
So yes, this is a big advantage FSX has over FS9, that as of today nobody else has exploited in this way, since it's probably easier to brag about a product having ultra-HD resolution, rather than explaining why is faster. In fact, KLAX under FSX is faster than under FS9 on the same system...