They did but honestly and maybe my eyes are deceiving me but the iphone4 screen i find is so much sharper than the One X especially in some apps ie temple run for instance...it looks washed out and blocky on the One X compared to the pin sharpness of the iphone4...could be that the iphone4 screen is smaller therefore better looking but i do prefer the larger screen of the One X, just find a lot of the apps i have downloaded just dont look all that great on the screen.
The dpi of the One X is more then enough that in theory everything should look razor sharp..
However, what resolution ,and therefore, what dpi any games/apps are natively rendered in can negate it all..
The difference in DPI is marginal (330 vs 316 in favour of the iPhone) so it's not the screen tech..