Well, to take MGS4 as an example:
Some cutscenes, like Big Mama's explanation, the end of Act 3 and the Debriefing were extremely entertaining to watch, so entertaining that I watched them on both playthroughs. Same with the opening cutscene.
Some cutscenes, like Snake meeting Drebin, I just about managed to watch once. I watched each cutscene at LEAST once, even if I was groaning through it, so I wouldn't miss anything.
Overall, I like them when the graphics are good, they don't repeat themselves, and they are interesting.