This is a great game with minor, distracting flaws.
The Good...
1. Great Story
2. Great combat, especially the arcing ablitiy
The Bad...
1. Awful way to gather resources
2. Minor bugs and glitches
3. A lot of loading
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Long Review
Mass Effect 2 is a very good game. With that out of the way, I'm going to start on why it is good. Mass Effect 2 has a very solid storyline. This storyline is even better if one imports his/her character from the original Mass Effect. Throughout Mass Effect 2 it references the first game. Additionally some options are not available if one hasn't played the original game. Will this hurt the overall experience? No, but when one imports his/her character into Mass Effect 2 then feels like it was custom made for you. A second great thing about the game is the combat system. This is somewhat deep and is very enjoyable. There are plenty of enemies to fight, each requiring a different approach to take down. Just the amount of skills and synergy in the game is impressive. Drop a singularity, then shockwave all units caught. Use pull on a unit then light them on fire while they are in the air. These are just 2 of the many amount of deadly combos that can be created with the combat system. Another great thing about the combat system is the ability to "Arc" skills around cover. By aiming slightly away from the target, the ability will curve in that direction before closing in on the target. This simple addition is extremely fun to use. Arcing a Incinerate over cover, then watching the burning enemy fall to the ground is extremely satisfying.
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Mass Effect 2 does have its flaws. Sometimes the A.I is stupid, usually resulting in the death of a teammate. There is also a lot of loading in the game, though this is just a minor distraction. Additionally there are some bugs in the game that annoyed me. Sometimes my character/teammates would start to walk in the air(if I walk off certain places) and I had one bug on the krogan planet where the person i was talking to just turned invisible. This only happened once, but it still is worth mentioning. Finally my biggest issue with the game is the way one gathers resources. The planet mining is awful. I hate this so much that I dread upgrading my character because I know I'm going to have to mine a planet. Even with the mining upgrade it is still horrid.