Since ME1 never came out on the PS3, the PS3 version of ME2 made up for the inability to import ME1 saves by including an interactive comic DLC (Mass Effect: Genesis) that makes up for the "missing" game by letting you make decisions that will affect the second game.
I assume an imported save from ME2 which had that DLC will take these key decisions effective in the third game as well, but I was wondering – are there are some actions available in the first game which I'm missing out their direct meaningful influence on the third game because I don't have a save with these actions performed? If so, is there a direct gameplay disadvantage (for example, missing characters, galactic readiness, etc).
Best Answer
You miss out on a few things, I'd only consider the interactions with Wrex as major:
There are more but most of them are simply war assets etc.