There is a lot of Kirk which is Shatner and Pine still managed to get those aspects by trying to play Kirk. His body language is very much like Shatner even though he isn't trying to emulate him because so much of the character was defined by the orginator of the role (shame about the film being so-so).

McGregor resembles Sir Alec's performance more in ROTS because he seems to be playing Obi-Wan more (a character created and largely defined by how he was portrayed in ANH).

The rest of the time he seems to be reading his lines while doing mental arithmetic only stopping to smile or frown on cue (the same with Neeson, Portman and just about everyone).

Jake and Hayden played themselves (not their characters) very well and I didn't like either of them.