The finance wiz have something they call the Time Value of [Everything]. So comparing ME1 @ 2008, ME2 @ 2010, and ME3 @ 2012 there is no doubt that ME1 stands head and shoulders well above ME3.
Mass Effect 1 brought me what no other game had brought me before it. The galaxy, the stars, the planets to explore, well that's just still pixels on my screen -- I'm not falling for that 'scale' hype. The true worth of Mass Effect is in the interactions and relations with well fleshed out squadmates and secondary characters.
Just like I make sure to buy the best weapons for my squadmates in ME3, I felt the connection with them better when in ME1 I actually had to set aside money to buy them the best armour as well.
ME2, game mechanics-wise, gameplay-wise, selling-more-copies-wise, ok, it's mostly something that stands on its own and serves to get us to wait for ME1 to continue.
It wasn't quite the sequel I expected story-wise.