I can't believe you haven't finished ME3.
I played Mass Effect for the first time less than 6 months ago and I've already played through the entire series twice.
I originally played through 1 and 2 on Xbox 360.
Then my Xbox 360 fried, and so I repurchased all three on PC. I spent some time trying to convert my Xbox saves onto my PC so I could use my same character (apparently this IS possible), but I eventually got frustrated and gave up, and played 1 and 2 straight through almost nonstop (ie, playing no other games).
Then when I got a couple hours into Mass Effect 3, I found I was a little burnt out.
I'm sure I'll go back to it eventually. Playing through the first two so quickly, with no time off in between waiting for the next release (as is what happened when I had first played them) I think made me a little tired of it. I felt #3 was getting kinda cheesy. But the series as a whole I would definitely classify as "must play." Hell, I'm trying to get a buddy of mine to finish ME2, I always harass him about it.