One of the physical drawbacks of OLED (Organic Light Emitting Diode) displays is that the manufacturing process can't quite reach the insane pixel density that traditional LCD makers can. We can argue about saturation, color representation, and pentile until we're blue in the face, but this particular issue is backed by real numbers, and because of it, high-end LCD displays like the ones on the HTC One X are more crisp and clear in some areas.
That all may be changing soon, if we're to believe a report from Korea that Samsung has perfected their FMM (Fine Metal Mask) production techniques to produce OLED displays at up to 350 ppi. In comparison, the iPhone 4S display (labeled as "retina") is 326 ppi. More pixels per inch (that's what ppi stands for) means cleaner lines on text and image borders, and is generally considered a good thing.
We'll keep our eyes on this one, and if it turns out to be true we should be seeing some interesting screens on Samsung phones late this year. We like interesting.