Yeah, Toon is right with all of that.
Personally, I still think that gaming has a way to go to catch up with film - too much attention is paid to the physics of the game, the visuals etc (well, obviously - it's a game!) but I do find that it's rare to get a genuinely brilliant storyline in a game.
Mass Effect - and particularly the sequel - rewrite the rule book. You care about the characters, and they are brilliantly written. Some of the best bits of ME2 is meeting up with old friends who you spent HOURS with in ME1.
If they ever released an ME game in episodic formats, it'd be torture - imagine beating a boss character, and not knowing what happens next until the next installment! It's one of those 'just 10 more minutes - shit! - it's 3am!' type of games. Time flies when you play it, simply because it's an utter pleasure to play through it.
It is also possible to argue over your favourite character with someone else who's played it. Whereas games might have one or possibly two pretty ace characters, the amount in the Mass Effect universe arguably reaches double figures.
It's just sublime and I cannot wait until ME3.