Imagine what it could've been though if they hadn't fucked up the ending of 3. People would've pointing to the ME series as the game(s) of an entire console generation.
When it comes to playthroughs though, I played through 1 and 2 like 3-4 times and I played 3 exactly once. That says it all, really. I know there's DLC and stuff that makes the ending more bearable/better, but I just can't bring myself to play it again after the letdown that vanilla ME3 was.