Hahaha... it's massive huh? DAO is well developed, but I find certain sections a bit draggy, and the travelling portions a bit slow in loading, and it slows down the game experience.
ME1 is fast paced. It's basically a well disguised shooter, with a very well developed storyline. I ended up playing ME1 a total of 11 times in different characters, but DAO so far only twice. That Dwarf bit is a bit tideous for my liking. Also, I find ME1 is far more engaging as a role player than DAO. The character development is a lot more interesting. Basically, they're similar, but ME1 is a lot faster paced. Not that it's a shorter game, because it's not.
ME2 is even more of a shooter, with a lot more tactical moves. I find that ME in general is better packaged as an experience than DAO.