based on composer credits alone I'd say that 1 is more like 2 than 3.
You'll note that while Sam Hulick does music for all three games, Jack Wall does 1 and 2, but not 3, and 3 adds a whole bunch of other composers, including Clint Mansell the wonderful (IMO) Cris Velasco.
Check out some of the Mass Effect 2 DLC albums btw, some of them are by the people who came on to the team for ME3.
(Reviews of all the ME2 DLC albums etc are forthcoming sometime in the next month or two)