I think a lot of the changes from ME1 to ME2 were really hit or miss. I know a lot of people didnt like the 'ammo' thing, but I thought it was pretty good. But I didn't really like the new mini-games for opening doors. At first it was cool because it was different, but it kind've got old. Same with the whole planet-scanning thing, its interesting at first, but it gets annoying after a while. I like how you can upgrade your weapons and armor and stuff with your resources, but given how annoying the whole planet-scanning thing is, it would be nice to be able to get more resources during your missions and such.
Another thing I didn't like was the lack of interaction between you and your teammates during missions, it was bad enough during ME1 but taken to a whole new level in ME2. I did like the main storyline, it was pretty good. I liked being able to meet so many cool new characters, and get to know them at least a bit. I really liked the whole 'loyalty mission' thing, that really helped you get to know them better than anything else, certainly much better than the on-ship conversations. I also liked Kelly, the new personal assistant. I liked how we sort of got to have a romance with her, the first time you could have something like a real romance with a non-teammate in any Bioware game that I can recall. Of course I know 'technicly' it didn't count as a romance, even though it had all the elements of a romance, but I guess if they called it a romance Mr Hudson would have to say that Kelly isn't really a woman, and the poor girl has been through enough, she doesn't deserve that

. But I hope they build upon that theme in the future, as it was REALLY well done, especially because you get so many brief little conversations with her, its nice that there's always something new that she has to say throughout the game, and the flirting is just so very fun and cool

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I really enjoyed getting to visit the Asari planet, and the Quarian Floatilla. It was nice going back to the Citadel, sadly there wasn't much left to remember. The Krogan homeworld wasn't near as interesting, it was OK and all, but certainly nowhere near as cool as the Asari planet, that was the best. I liked how they did it with the big final mission sequence, all the choices you get to make in an effort to save the teammates you care about. In my first attempt I was able to save everybody I really cared about, and everybody I cared at all about except for one, still don't know how I managed to lose Legion the way I did, but its no biggie. I just wanted to save Tali, Jack, Miranda, and probably Samara, really the rest of them were totally expendable (lost Thane and Jacob also, but didn't care) . I'll probably try to do a run where I save everybody at some point, but in any event it was fast-paced, very well done, plenty of mystery behind what the right decisions were, two thumbs way up for that. The final battle was rather a joke though, maybe at that point all you really want is to see the ending so an easy battle is OK, but it was just so insanely easy, it was like the world's biggest floating target flying around, you shoot it for a while, and then the battle is over.
I think the whole variety of weapons thing was REALLY cool, its a shame that didnt carry over to the outfits. I had ONE outfit that was even slightly worth wearing on the ship, and nothing really good. Happily at least the armors were color-customizable, that was a nice touch, and I was able to get a really cool colored armor as a result

. I suppose the biggest negative in the whole game was the way that the romances were done. The ones that carried over were given SUPER little time, and the new ones were done horribly wrong for a lot of players. It was a bit....odd....the whole 'new Liara' thing, but I think I got used to it faster than most, I would like to know more about what caused this new outlook, but Im not dead-set against it like some seem to be, I think it could end up being quite cool. But for those who did romance Liara, how did we end up with nothing but male LIs in ME2??? Obviously MaleShep players who romanced Liara didn't experience this problem, but FemShep players certainly did, and it was quite horrible. Obviously anyone who romanced Liara in ME1 (and ME2 reads your save game and knows if you did) should be given female LIs, not male ones, unbelievable mistake that results in all of us having no new LIs at all (other than Kelly of course), which of course is totally inexcusable .
The best part of the game for me, was such a surprisingly large number of things that you did in ME1 showed up in some way in ME2. It was extremely cool seeing all those things, some big some little, playing some kind of role in the game, I was quite surprised they were able to use such a large number of things from ME1, it really added a LOT of coolness to the game! I especially liked meeting the Asari girl from the planet where you defeat the Thorian, I'd like to meet her again in ME3 (especially given the way the conversation went, sounds like a future meeting would be lots of fun)

. Meeting that other girl, the undercover girl who you help bring down a criminal dude in ME1 and an Asari criminal girl here in ME2, she was cool too, Id like to see more of her also. So many details were done so incredibly well, it was quite the surprise that any game could do something like that, and hopefully they'll be able to do that again in ME3!
So the bottom line is that certain things were done better, certain things were done MUCH, MUCH worse, and some extremely cool and unique stuff was added. It was very hit and miss, and the bottom line for each player will be in determining whether the good outweighs the bad. For me there was enough good to say it was a fun game, but too much bad to actually reccomend it to my friends, and thats different than ME1, which I highly reccomended to my friends. Im hopeful that ME3 will continue the many things that were right with ME2, and change the relatively few things that were not, so that I can once again highly reccomend it to all my friends!