Well... completed ME1 a few weeks ago, and loved it. The last sections had me up till 5am the story just kept me going. There were tedious bits, like taking ages to drive around on planets on the mako, and having to randomly try and find minerals... but overall, a very enjoyable game. Story was excellent.
ME2 I completed that last night... well I think the changes they made to the squad and combat systems were not that good.. I think the ME1 system was slightly better. And planet scanning.. arghhhhhhh. Just so tedious, but it had a purpose... a little work to get some upgrades. Other things I didn't like about ME2.. were the relative lack of customisation. ME1 was much better, and gave a much bigger variety of armour and looks. Also.. a wierd thing.. I though Joker 'looked' better in ME1 than ME2. I felt that ME2 was generally dumbed down compared to the first one.
However.. I liked that they tried new things with ME2 compared to the first one, although I despised working for cerberus lol. It also seemed less story driven. (Did anyone else think the 'fuel' noise for ship was wierd in ME2?)
that sounds just about the general consensus on them both.