A biased review due to some basic issues with the game.
I believe this game would be much better if played on a large HD display. If the player had perfect vision. If the player has at least stereo sound or a higher quality sound system. If you have a regular TV set which is of average size you could become very aggravated or not even want to start playing the game.
Mass Effect 2 has a lot going for it. The game has a great deal of depth. The characters have their own personalities and the game does a great job of capturing their good and bad sides. You may dislike a character while at the same time laughing at their dialog. I appreciate the amount of time that went into the people you will be playing with in the game. You will need to find your crew and to make them loyal to your command.
The game also features a bit of an economy. It's nothing major but is welcome in any game. There are not only item upgrades but souvenirs and other items you can purchase. The shops are spread out in the galaxy you are traveling and add to the diversity of the game. You get most of your money by playing missions and helping out others. Mining of minerals is something you will need to do. Some people may not like the monotonous way this is done but I didn't mind it. It gave me a chance to play some of my own music and play at the same time. It was a simple task without stress. Unfortunately you can't sell the minerals for even a few credits. I actually would have done more mining if this were the case. The economy was very controlled and you will always be looking for more money to buy items.
The weapons have some real variety. I personally liked the sniper guns which let me pick off the enemy from a distance. The need for some close in fighting skills is also necessary. At times the enemy seems to pop up out of nowhere. You will need to do some fast thinking of how to get away and heal up. The player's health and shields will improve due to upgrades throughout the game. The leveling system used it fairly simple but mechanically it could have been handled a little better. Still I applaud the ability to change your character later if you have messed up the build.
I enjoyed the missions but didn't like missing items or money. This made me search the entire mission area. I wish a few more enemy would pop out even after the main fighting was over but they will always come to you. Searching all of the missions eventually made me feel like it was a time waster used to add length to the game. It had the effect of ruining the game's flow. Maybe having a larger HD display would have helped here but I doubt it. The mission will end and give you a summary of what you did and found. I would compare this to the Mass Effect wikia site to see if I had to redo the mission due to missing an item or money.
Overall the devs did a great job with this game. I enjoyed it and wanted to play. I could not enjoy it completely due to my lack of a good entertainment system and HDTV. That should not be a limitation but maybe Mass Effect 2 is a game that will be purchased years down the line. Maybe the game is a little ahead of the curve but for me it was a bad design choice. I just wanted to get back to the action. The voice acting kept the game engaging but the verbosity needed some tweaking. I eventually began to get tired of all the vocal choices on screen. The character building of your main character was great. I made a character who was as hard headed as it gets. Unfortunately they still could not do all the "renegade" dialog choices. That was a bit of a let down. The game is worth playing and I can recommend it especially if you have a great TV. If you don't then you may want to pass on the purchase.