I havent played it, but I would say yes.
Even if it was called Lost Odessey it could have still sold 4 to 5 mil copies in my opinion. The problem is it came out as a console exclusive for the 360.
Where there was not much of a JRPG userbase. And it was very early title, competing with titles like Halo and Gears of War.
So it just got lost in a torrent of unfortunately circumstances.
If Sakaguhi made an RPG today and released it for the PS3 as the main platform of release (not the Wii) I have no doubt that game would sell about 4 - 5 mil copies. His name carries still carries a lot of weight. Sadly he only seems interested in mobile phone games now!