I've never really torn into ME2. And for those who have read my opinions before, you will probably guess the next sentence: because I never actually beat ME2. ME2 is a shadow of its former self. It is completely forgettable.
A lot of people will claim ME2 is streamlined and that is good. However, I will posit that the combat still absolutely sucks in ME2. So, you lost RPG elements for what, for nothing? You didn't gain better FPS elements or better action/adventure elements. You just got a lighter, more shallow RPG. On what grounds can I make such claim? Easy, Dark Souls, here is a series that has more RPG elements than ME2 and more action elements. Beaten on both fronts. The only genre that ME2 brings to the table is "story telling", which really isn't a gaming genre so much as it is emulating a movie.
We excused the combat in ME1, we excused the combat in Kotor, we did this because they were RPGs. Once you eliminate the RPG aspect, you can no longer excuse the tired, unimaginative combat. More so, limiting ammo at a disgustingly low amount is not a valid way of balancing the difficulty of your game.
The problem with the gear in ME2 is that none of it is substantially better. So besides a few skill upgrades, you are really as strong as you will be at the start as you are at the finish. Which is great from a "do things in any order" viewpoint, but terrible from a "well I'm really good at this game, it isn't going to get much harder and the story isn't really gripping me, so I'm going to put it aside and pretend I beat it". Should I need to be challenged? Well, it is a video game, and that is usually the crux of video gaming.
The other problem I have with ME2 is that they removed one of the only unique elements they had going. Planetary Exploration. This one hurts me a lot and, aside from a better story, is the main reason I love ME1 so much more than ME2. I really enjoyed planetary exploration, it made me feel disconnected, alone, remote and it made me feel like I was really exploring space. The exploration feature wasn't perfect in ME1 and was best implemented in the moon mission DLC, which really worked hard to fully populate a planet with interesting things to do. Going into ME2, I thought the moon mission from ME1 would be the template for planetary exploration. But instead they scrapped most of the concept completely. In fact, one of the only missions I really enjoy in ME2 is where they brought back planetary exploration, I think it might have been a DLC, for some planet with lava.
For a comparison, I recently revisited my backlog and completed STALKER:Call of Pripyat. I revisited this before ME2 and Fallout:NV and many others that I've only partially completed because CoP challenges me. Both CoP and ME2 took me back to a common environment and let me revisit it. And even though CoP is a foreign game with terrible cutscenes and reused almost 100% of its artwork, I still felt more engaged, more challenged, even at the end of the game I was still trying to figure out how to improve my character, what weapons to upgrade and how to improve my tactics against various enemies.
Someday I will finally truck through and finish ME2, hopefully the last 40% of the game some how surprises me and I can eat my own words.