I felt the first game was over-rated, in particular I felt that only a few of your party were interesting. It's story didn't engross me as much as KotOR, and the decisions didn't seem to carry enough weight to them. Don't get me wrong I enjoyed it and have completed multiple playthroughs (+all the DLC), but I don't think it was so great that no sequel could have compared to it.
The second game brought some needed improvements. I like the ME dialogue system (it felt kind of jarring to have a silent protagonist again in DA:O after ME), but Hawke's voice actors weren't up to the standard of Sheperd's. Overall I liked the party more, Varic and Isabella especially - though Zevran's cameo reminded me what a fun character he could be.
The biggest problems for me with DAII was that the whole game felt rushed and unfinished. I encountered a lot of bugs, including unfinishable quests and the Isabella slow down. The limited use of environments and endless fetch quests made the game very repetative (even to a die-hard completionist like myself).
Finally, the plot was both unconventional and structurally odd. I think Bioware deserve some credit for trying something different - Hawke is a hero carried along by circumstances beyond his control (rather than the more traditional reshaping the world role RPG heroes tend to fall into). Unfortunately, I don't think it paid off. The final act feels disconnected from the rest of the story, and Hawke's decisions are disappointingly binary.