I have finished more than 30 xbox 360 games and ME2 BLEW ME AWAY!
Its not even the fact that the 3rd person shooter elements are better than those in Gear of War 2 and the weapons range extensive. Its not the awesome RPG and upgrade elements that are top notch or the AMAZING story and magnificent graphics, but its the characters in ME2 which are the real stars .....they will steal your heart. I really started to care about them and look forward to seeing and interacting with them every time I played and that is rare. An emotional connection with the story of game.
The missions are just the right length and everything feels polished and thoroughly tested (TAKE NOTE FALLOUT NEW VEGAS). They nevver make you backtrack through environments when you have completed your objectives and on top of a 35 hours campaign the game has HUGE replay value and there is downloadable content. I played as an Infiltrator first time but am itching to do another play through as a different class. The game also gives you the option of running the campaign again after you finish with all your experience and upgrades retained!
If you have played a bunch of mediocre games recently (like I had FEAR 2, WOLFENSTEIN and FALLOUT NEW VEGAS) this is the game that will remind you why you started playing games in the first place. This is the massive game you've been waiting to be obsessed with, that will invade your dreams and steal your nights and you will thank it for doing so.