Despite giving the series an "E for Effort", one of the editors at Destructoid has penned an article that points out many of the issues he has with Mass Effect and Mass Effect 2. There will obviously be some disagreements over said points, but here's a bit to start you off:
Mass Effect 2 has been called the Empire Strikes Back of the series. I disagree. Its more like the Matrix Reloaded of the series. You start off with your ship being blown up with nearly everyone but you alive and well. Thankfully the evil Cerberus comes along and glues Humpty Dumpty back together again. You are then introduced to Miranda who doesn't like you and Jacob who does. Mass Effect 2 in fact throws a bunch of new people at you from the beginning and hopes that you like them -- Martin Sheen being one of them. The game then forces you to join Cerberus and gallivant off to some new hell hole called Omega that also has the biggest relay in the galaxy. You pick up the cream of the crop of the universe and head off to stop the collectors from terrorizing human colonies while learning that Cerberus isn't all that bad. It all ends with a super fight against a giant Terminator.
Its a bit over the top and has only a few things tying it to the original, but it's pretty and "epic". Kind of like Matrix Reloaded. The biggest issue is that I never once felt my crew was going to die. Everyone from bloggers to Bioware went out of their way to tell me that my choices will potentially kill all my teammates. Nobody died. I never felt that anybody was going to die. I just pushed it up to my team making bold statements and then everyone will come through.
There are a lot of things I don't like about Mass Effect 2. None of the worlds are particularly interesting. They have cool features, but they aren't as interesting to go through as the first game. The Citadel which was kind of cool is now a Mega Mall. I became a Specter again only to not have any reason to. Ashley was fucking pissed that I was Cerberus even though I didn't want to be on their team. Liara, one of the foremost experts on Reapers, is now a shadow broker for some reason. I honestly hate that. Hell, I was expecting her to reach out and try to stop me on my supposed suicide mission. Actually I was really expecting her to have become pregnant with my child; something to throw a real consequence to the relationship tree. Nope. Peck on the lips and then straight to normal business. I wouldn't have thought we'd had sex if I hadn't seen it in the first game. The first games only main crime is that its potential wasn't near what the seconds was. That isn't something I can fault the first game in a series for though.
The last thing to talk about is DLC. I bought Mass Effect as a Platinum Hits because I just shrugged and said what the hell. It came with the "Bring Down the Sky" DLC as a code from the outset so I view it as a part of the game. It was probably the best part of the game as I usually ran into it after leaving the Citadel. There is a real consequence asked and a really cool item gained. Unfortunately I didn't run into any Batarian warlord in Mass Effect 2. That was pretty annoying.