CGI: Bioware games have not been seriously underestimated since the Baldur's Gate days, I'd rather say that some of them are overestimated before they launch and a lot of reviewers overlook a lot of problems simply because its Bioware (reviews of ME and Dragon Age showed me as much).
Seriously, everyone and their dog expects ME 2 to;
A: Blow everyone away, me included if they get everything right this time around
B: Be among the strongest candidates for GOTY
In the end though, Starcraft II is still the strongest candidate imo.