me2 had some nice character moments, but its main plot was very stupid with ridiculous reasoning that threw away all appeal of me1. Best elements of me2 (and me3!!) were stories that expanded the stories, already established in the first game (genophage and quarians/geth conflict).
It's weird to see so much praise for ME2 everywhere. I hated the game after ME1. There's basically no main plot. 90% of it is side quests to flesh out side characters. Which, fine, I see why people enjoyed so much, but it felt so pointless to me because the main plot boils down to "throw all these people at a final base and see who makes it out alive". I wanted to see the ME story moved forward, but it took until ME3 before that actually happened.
Also, ME2 committed character assassination of Liara, who, for some reason, unexplainably turned from a nerdy aecheologist into a deadly spy assassin. And the game railroaded the player into working for Cerberus. Ugh.
'lets build this McGuffin thing that we conveniently found at our doorstep at the very right moment and which we aren't even sure how it would work, but we will use resources of the whole galaxy to build it' story was hardly any better.
In the movie Contact the Earth wasn't under a genocidal attack by a overwhelming forces of a highly advanced alien race, they just received some blueprints that they thought should do something. And It was at least known how to activate the thing. With Crucible, they didn't even know until the very end.
To anyone who thinks ME2 is better, I can only recommend this mighty analysis of the series: https://www.shamusyoung.com/twentysidedtale/?p=27792
Lots of parts, but it highlights all the problems of the second and third games really well.