I describe Mass Effect 2 to people whom ask me about it or speak to me of it, as the original Mass Effect with a few things fixed and most of the compelling elements of the original that appealed to me taken away.
I have to agree with Yahtzee on one very pointed example - the vehicle sections. Yes, the preternaturally indestructible Mako felt like it was bouncing around on massive air cushions, but the vehicle sections gave the game a sense of scope and bigness, and it rewarded the explorer and the roleplayer in me. Mass Effect 2 took this element out and suffered greatly for it, indeed, again as Yahtzee said, the game feels very much like a collection shooting galleries rather than flowing between different locales. It feels more like a JRPG with ambitions of being a shooter in that I feel like I'm only really there to direct the character from one scene to another while watching the comparatively bland exposition unfold. This is not to say that the dialogue is bad - it is in fact rather good, if a bit skewed because of the horrid moral choice system that gets shoehorned in - but rather that compared to even the original of the series, Mass Effect, it seems lacking, and lets not even begin to compare it to KOTOR, NWN, or the Baldur's Gate series.
The combat in Mass Effect was kept somewhat lively because of the great degree of customization the characters were afforded, and the challenge of developing not only a self-sufficient and powerful single character, but also in balancing a team that complimented each other's strengths and weaknesses. Mass Effect 2 takes that variety out to the back and basically gives it a pair of concrete shoes to wear before tossing it in the deepest portion of the Marianas Trench. It is repetitive, boring, repetitive, nothing we haven't seen before, repetitive, and I really didn't enjoy it. Did I mention it was repetitive?
Really I expected better out of Bioware, but they seem to be suffering from the EA syndrome lately. Lets hope they pull their heads out of the sand and develop at the level they're capable of - because as a studio they've proven they can push out some real gems and it would be a terrible shame and a loss to see them go the way of these companies that rush out utter bollocks to make a profit and squeeze a series well beyond its worth.