Some of the dialogue is repeated for all three, but Alistair's lines, because of his personal involvement in the 5th Blight and knowing the HoF, gets special lines the other two don't. In particular if he was romanced. My Warden Alistair WS was a King Cousland, and he wasn't romanced, of course, but he even had special lines for that. Kind of saddened me actually. I ended origins with the two of them as close as brothers, but apparently 10 years created a breach between them. He said my boy was 'following a dark path'--which I think probably meant an allusion to the Dark Ritual, but still the way he spoke of him, not very brotherly/chummy.
Leliana spoke the same romanced lines (since I romanced her) that Alistair gets if you romanced him and kept him a warden in Inquisition. Have to say I prefer Romanced Alistair's warden cameo, although his king cameo in the game is awesome. Not going to spoiler any of it in case anyone hasn't done Inquisition yet, but both are really good.