It's handily the worst game in the series. Not terrible, but a major step down from the first Mass Effect. Thankfully Mass Effect 3 remedies all of the issues with Mass Effect 2 (and the first game), but why all the praise? I don't get it and if anyone has an explanation I'd like to see it. The issues I have:
It's terrible. Levels are not only short, but they are all tiny little hallways. You literally jet forward the ENTIRE time. Good luck trying to explore anything. Sure, ME1 has levels that are larger but not necessarily as well designed, but that game was more RPG and less action anyway. ME2 goes for more action, but the level design is a joke. It's thankfully much-improved in ME3 as there are major combat areas that you have to be fully aware of while fighitng.
It's terrible. Enemies follow set scripted patterns that they repeat EACH TIME you play the game. They also respawn if you leave a room and return to it and again perform the EXACT same actions as before. They are literally cannon-fodder and present no challenge as you hunker behind cover and they pop up to shoot at you without really moving. It's sad. Thankfully, Mass Effect 3 has enemies that actually provide more of a challenge on normal than the previous two games did and they do so by utilizing their environment (going back to level design) and often flanking you if you aren't properly taking control of the battle.
Bosses are in the background
By this I mean they are not on your playing field. Also, it's terrible. In Mass Effect and Mass Effect 3 the boss is on the same ground as you. They move on the same plane as you and they pose more of a personal threat. In ME2, EVERY. SINGLE. BOSS. is a cutout in the game's background. Granted, this might be because the level design is so constricting and poor that if they added a boss character there'd be no way to properly manuever. But prepare to hunker down behind a rock and pop up and shoot the floating face of doom in the background. Don't worry, it's not going to jump over your cover and melee you in the face. It doesn't have that capability.
Mass Effect 2's existence was made relevant to me when I saw that its characters provided much of the emotional punch in Mass Effect 3. But as a stand-alone experience, Mass Effect 2's narrative is extremely poor. I know many folks say it's essentially Seven Samurai in space, and how people shouldn't criticize this game for its story as Seven Samurai is considered one of the most exciting movies ever made.... BUT, Seven Samurai, The Magnificent Seven and 13 Assassins are all movies that get this "suicide mission" thing right and Mass Effect 2 doesn't. You spend the majority of the game, I would say 90% of it, though that number can be argued so who cares, I'll stick with majority, recruiting team members and gaining their loyalty. You then spend maybe an hour on a so-called "Suicide Mission."
Folks, Seven Samurai spent half the movie recruiting members and the other half in the conflict. The reason why it's so exciting is not because we watch 2 hours and 45 minutes of recruitment and 15 minutes of defending villagers against the bandits. ME2's conflict is almost non-existent much of the time. Aside from a few missions where the Illusive Man tells you "hey man, we saw some Collector's here!" you're literally playing house with your team.
Jacob- "Shepard, I know we have this suicide mission, but man, I can't give it my all, cuz, you see.... I'm looking for my dad."
Miranda- "Shepard, I know we have this suicide mission, but man, I can't give it my all, cuz, you see.... I'm looking for my sister."
Thane- "Shepard, I know we have this suicide mission, but man, I can't give it my all, cuz, you see.... I'm looking for my son."
Samara- "Shepard, I know we have this suicide mission, but man, I can't give it my all, cuz, you see.... I'm looking for my daughter."
Grunt- "Shepard, I know we have this suicide mission, but man, I can't give it my all, cuz, you see.... I'm hitting Krogan puberty or something, man."
Jack- "Shepard, I know we have this suicide mission, but man, I can't give it my all, cuz, you see.... I'm looking for my shirt. This strap is really cutting into my nipples, y'know? And I mean, I know we're all about taking this seriously, but WHO DAFUQ took my damn clothes and left me with nothing but a leather strap in space! It's freaking cold, man!"
In ME1 and ME3, the conflict is always around. It's front and center throughout the game. In ME2, the conflict is an afterthought, essentially making the game Short Stories in Space (sometimes with a silly twist).
The Suicide Mission
Talk about a disappointment. The Suicide Mission is longer than any other mission in the game. That doesn't mean squat. There's no emotional attachment to it. It's like a series of set pieces that lead up to one of the lamest final boss encounters in years. It's neither challenging nor exciting. Just a romp down a bunch of brown corridors. I do give it credit for utilizing the full squad, which is neat as usually Mass Effect sends out two people with you and everyone else twiddles their thumbs on the Normandy, rather than, you know, being badass like they should, but whatever.
Mass Effect 3 avoids all of these issues, and Mass Effect 2 essentially works as what can be the emotional core of ME3. But so much of it just so poorly done. I don't understand why so many people think it's so amazing. And I get that people don't like Mass Effect 3's ending, but that isn't reason enough for me when it's the far superior game (and I didn't mind the ending). And I get that people hate Mass Effect 1's Mako sections and barren planets (they are kinda dull). But again, that isn't reason enough for me on how a game that screws up the fundamentals is so highly praised by so many people.
EDIT- I forgot to mention planet-scanning and probes..... oh man I hated that.