Well there are several timed mission in ME2. You have to look at the evolution between ME1 and ME2 first. While ME1 was RPG with a bit of FPS thrown into, ME2 is the exact opposite. And the improvement is incredible. I've played ME1 once, because of it's great story and setting. I've played ME2 because of it's incredible gameplay (and also story and setting). While I agree that there can be much improved on some of the action set pieces, there is hardly any game this gen except for Uncharted 2, which does everything on this level of quality.
ME2 and UC2 are two greatest games this generation.
MY HYPE LIST: 1) Gran Turismo 5; 2) Civilization V; 3) Starcraft II; 4) The Last Guardian; 5) Metal Gear Solid: Rising