It's a weaker game in concept to its predecessor, but it's perfect in execution, and that's all that matters in the end.
Graphics: Some elements seem dated, but as a whole, the game is miles ahead of anything else out there. No slowdown during battles and far too much going on at once.
Sound: Great. Every line is recorded, as it was before, but the voice acting is noticeably better. The only weird part is the illusive man...his voice just doesn't fit his face.
Story: The main story is bit of a letdown, but the side-stories make up for it in spades. Of particular note is the story of the Drell Assassin. If you don't like it, you have no soul.
Gameplay: It's not a great RPG or a great shooter, but in handling both well it ends up being absolutely great. It's shallower than Mass Effect 1 on the RPG end, and I really wish they hadn't pulled the Mako and the weapon mods, but on the whole the concessions made are ok. The new game is faster, leaner, and most definitely meaner. Just remember that it is an RPG, and while twich reflexes certainly help, timing and attack choice are vastly more important.
Mass Effect 2 is a stepping stone. Provided that Bioware ramps up the complexity to a nice middle ground in the third installment and keeps this level of polish, the game will be the best ever. Until then, we have a game that deserves the perfect 10 for what it does, but really should have had more in it.