Jacob, Miranda, Grunt, Zaeed, Kasumi, and Legion had terrible attempts at chemistry and the DLC characters didn't even have dialogue options. The rest of the characters didn't get great stories until the third game (Mordin and Miranda especially had nice improvements by then). There were just to many dead weight archetypes trying to fill the game up. Maybe Thane, Jack, and Samara had good missions, but the rest were rough. The 2nd game was throwing every character idea at the wall and desperately hoping they'd stick despite lacking the much bigger stories the original game's squad were each related to.
The original squad had one mission each at best which generally were terrible? (Wrex's 'go get my armour' mission in particular). ME2 had character missions with zero combat and pure character development, whereas Me1 missions were just more cut and paste stuff?
I mean, don't get me wrong I loved ME1 and the drama and storyline it had, but in terms of character writing and development I think Bioware learnt huge amounts from that game about what makes a good character and implemented it in ME2. Garrus and Liara are such different, and better developed, characters by the end of ME2.
(Plus, none of the characters had the emotional impact of Mordin and Thane in ME3 for me, despite being around longer).
I mean, I get that people prefer Me1 to ME2 - I don't, but I can understand why. But I can't understand thinking the characters in Me1 were better. Also worth remembering that your characters, and involvement with them, had a much bigger part to play and pay-off in Me2s end mission compared to Me1, where it didn't matter who you brought and the dialogue you got depended on the order you clicked on them (so I had Ashely telling me to save the Destiny's Ascension, and Garrus telling me to let it burn which make no sense at all in the slightest.
EDIT: oh gods, this isn't the ME community thread. Apologies folks will stop posting about ME here unless it's LGBT stuff!