Aren't the cutscenes about half (or more) of MGS games? They're almost more movies than they are games. I don't mean to be dissing them, because I enjoyed watching the MGS games on youtube. =P In fact I plan on buying Twin Snakes for the GC, I never even knew about it until now.
It does seem like you'll be missing out on A LOT if you skip the cutscenes. That's like only watching the cutscenes of Mario games and skipping the gameplay time. =P