ME2 is a step up from ME1 in many ways, but the story is weaker and it just manages to accomplish what was advertised.
Bioware clearly aimed to make the same impact with ME2, but several aspects of the game are lacking--namely the story. (As long as there are coherent plots in our video games, we tend to ignore talking about the strengths and weaknesses of these stories.)
Start expecting twists from the get-go. (May I remind you that the trailers point to Shepard's death and the destruction of the Normandy?) Most of them involve your new and old squad-mates alike, though most aren't significant.
What occurs usually is this: You find a potential recruit for your team, you bail 'em out of a bad situation by killing villains who are after said recruit, and the unique recruit will agree to joining you. Having seen the character trailers, I was quite disappointed to find how easy it is to get these assassins, soldiers, and asari justicars to join up with you.
There is little dialogue about leaving their past lives behind...probably because all of the characters are sad ones who have nowhere and nobody to return to. I am serious when I say that these characters are generic.
With all of that said...
Mass Effect is more of an FPS than it is an RPG now. There is no inventory system, and you find a few permanent, switchable weapons that can be switched in or out at your armory. The same goes for armor. You'll not be finding a lot of different armor sets, though you will be finding several individual parts of (nearly stat-less) armor that you can customize cosmetically.
These changes are for the better, because ME2 makes up for the lack of RPG features with superior FPS mechanics; their is ammo now, and the aiming and recoil is not affected by your skills. The weapons feel realistically responsive, to say the least.
Character classes have been streamlined, and hybrid classes aren't simply classes that share other primary classes' skills. There are far fewer powers this time around, but every class has a unique, defining ability. Infiltrators have a tactical cloak, vanguards can charge through tangible objects to smash into the opposition, and soldiers have a slow-mo ability. Heavy weapons are also a new addition, and they are welcome because of their versatility.
Mining and resources affect heavy weapons and are responsible for your researched upgrades. this time around. You may fly to other systems to scan and mine planets for a total of four different elements.
But what of the planetary exploration? What of the anomalies?
They're gone, for the most part...along with the Mako. If you do land on something important, you will be almost automatically engaged in combat. There is no need for much walking and exploring, as you'll have landed somewhere in the middle of hostile territory that is largely unrepresentative of the planet. Bioware opted to abandon the planetary exploration (it was dull), and although I would have likely done the same--it hurt the game. See, the game already feels ridiculously short for being at least thirty hours long.
I don't know anyone who would be able to quickly make sense of that statement, so i'll elaborate. There are about three or four missions that actually (directly) involve the main antagonists, and everything else will be missions and side missions for your teammates (usually optional missions that are done to gain their loyalties and special abilities). You'll spend a little bit of your time fighting your way to whoever you wish to recruit, and then you will receive ONE loyalty mission for each recruit as the story progresses.
If anyone is not aware of this already, your mission is to form a formidable team to fight a nearly impossible enemy. As it turned out, the "suicide mission" really only refers to a regular old story-mission. When all is said and done, you won't feel like you accomplished much even though you spent thirty hours; you basically spent 25 hours recruiting and making your crew happy and 5 hours doing the main missions.
It's funny, because right when you think everyone is settled in on the Normandy and ready for battle--they might all just die. I expected us all to think that the suicide mission was a...larger one that involved several smaller, dangerous missions. What less do you expect when the game tells you you'll be traveling into a part of space that is uncharted and dangerous?
One good thing about the story, though, is the fact that it is darker. The ability to interrupt someone while he is talking to smack him is a testament to that. Furthermore, there are many more opportunities than in ME 1 to choose between renegade and paragon actions.
Yes, this is the middle of the trilogy, and yes--I am aware of the fact that this game should be the setup for the final game...but why include one small mission at the end? To lead into the last one? To give us a hint of how much more dangerous Shepard's mission will become? I would've suggested not possibly having your teammates die, then. Many will not feel satisfied with playing the sequel that serves the purpose of bridging things from one game to the next. (I'd rather watch a short movie.) The characters are cliche and it's all not very interesting.
If you want something more fun to play than ME 1, look no further than ME2. Just don't expect to feel like you've done a whole lot in the thirty hours you spent. There is a point to centering this game around recruitment and preparation, but it just feels overdone and redundant in the end. But, like they say, you can't always have the same, fresh plot from the first game in the second one...