Besides the excellent characters, ME1's main attraction was its storyline. The beauty of it was not necessarily the story in and of itself (even though that was top-notch too), but more the way it unfolded. You started the game thinking you were fighting off a random geth attack, but soon you find out it isn't as random as you thought it was; Saren seems to be leading them.
Okay, you think, we'll have to find out why Saren is doing this, take him down, and be done with it. Right at the moment you think you've got it all figured out, it turns out there's something way more sinister and grander going on: you learn about Sovereign, this massive sentient ship that's controlling Saren against his will.
Okay, you think, so we take down Saren, then Sovereign, and be done with it. Just when you think you've got it all figured out - again - you talk to Sovereign himself, and Vigil, the Prothean VI, who explains what's really going on - and suddenly you realise you're in way over your head. Sovereign is but one of many, a race billions of years old that has been eradicating civilised life in the milky way every 50000 years for millions and millions of years - they're the Reapers.
The technology of space travel, the mass relays, the Citadel; all built by the Reapers to ensure that civilised life will evolve along the paths set out by the Reapers. Sure, you destroy both Saren and Sovereign at the end of ME1 in one of gaming's most epic battles, but you know it's only the beginning. The Reapers will come, and you have to be ready. You still don't know why the Reapers do what they do.
Mass Effect 2 suffers from being the middle child, I suppose. It doesn't have either a real beginning or a real end, and the story itself pales into insignificance compared to ME1. There are no big reveals here that have you shaking in your boots, there's no equivalent of the mind-blowing talks with Sovereign and Virgil. There's this tiny reveal of the Collectors being repurposed Protheans, but that's about it. If you blink, you'll miss it.
In ME1, you started out with a lot of questions, and every time these questions were answered, you only ended up with more questions. This is what kept you playing, and this is what kept me jumping up and down in anticipation while waiting for part two. Mass Effect 2, however, gives you a number of questions at the beginning, but it doesn't answer them, nor does it provide any new questions throughout the game. I kept on hoping for big reveals, answers to questions leading to more questions, losing myself in a story far grander than myself - but it just didn't happen.
Before I knew it, I was staring at the end credits.
I do it out of love
I commend you if you're still with me after me going all philosophical about a game franchise. It might seem as if I hated ME2, as if I'd never recommend it to anyone, as if I had a really, really bad time while playing it. That I want my 64 EUR back.
This is decidedly not true. ME2 is a great game, and it'll be hard for anyone to top this in 2010. It's a great experience to go through, well-designed, and a number of key aspects of Mass Effect 1 have been greatly improved. Sadly, there's also a lot that suffered.
I'm writing this not because I want to tear the game apart, or because I want to disparage the insane amount of time, work, and love BioWare employees have put into it - no, I write this because I love Mass Effect. I write this because I love BioWare. I write this because the reviews I've seen so far seem to be, as usual in modern-day gaming media, shallow, void of details, soft, filled to the brim with default adjectives like "compelling".
I'm the Mass Effect equivalent of the Trekkie, and the franchise has a very special place in my heart, right next to Fiona Apple, coffee, the Gilmore Girls, and the colour red. As such, I'm also incredibly demanding, and while I know it's impossible to please fans, I do feel compelled to put my critique out there - not to be a jerk, but to make sure that BioWare will make Mass Effect 3 even better.
I can't wait.