Look I'm pretty sure by the game announcements posted in 2005 by multiple companies, this was ALWAYS meant to be a trilogy.
Exhibit A:
Rich and engaging storyline. While defending galactic peace and earning a position of respect for humanity in the community, gamers will discover that a greater conflict between organic life and artificial intelligence exists. Players' decisions and actions will serve to shape the destiny of all life in the galaxy as you become absorbed in the story that is "Mass Effect," the first game in an epic trilogy from BioWare. They will become the center of an engrossing story as they battle against alien life forms to save the galaxy from threatening armies.
This was taken from a post on October 4th, 2005 on teamxbox.com. People are talking about this being a bad trilogy before they even see the end of it.
As for the discussion I was having earlier, my bad on the synthetic life cannot evolve. What I meant is that in order to have intelligence and take actual form it would need to be built. I know that this is applying real world logic to a game world that could be much different, so I could be wrong.
Reapers could be the result of a program/system becoming self aware (Terminator again), or even an AI that decided to preserve its own life, etc. I guess my point is I don't see how the thing could just become a Reaper without some kind of organic first creating part/all of it.
Now for the Cerberus thing. I guess I'm playing a different game like someone claimed earlier, because I never felt like it was forgotten how evil they truly are. What choice does Shepard really have after waking up from being dead 2 years in a Cerberus lab? He never calls out Cerberus for past events but what would it accomplish if he did?
The way I felt was that he and Cerberus knew that he did not trust them. He also knew that they gave him the means to get back into the fight that he never got to finish due to it killing him 2 years ago. By the end of the game many more things happen to make you trust them even less, and your crew sees this.
If they brought up the Akuze thing in THIS game, how could you possibly have progressed with the working with Cerberus gameplay? Its not like they had 2 more DVD's to write the "Shepard works for Alliance because of Akuze" version. That would be better used in the beginning of the third game as a way to put Shepard back into the Alliance.
They do a good job of not showing you black/white stuff, instead making you sort through the shades of gray to figure out how you feel about them. In the end you can choose to A) Abandoned Cerberus and blow up their ultimate goal leaving them with nothing to show for their investment

Side with Cerberus and the belief that to win you must be willing to sacrifice anything. Doing this will deliver a potentially devastating technology to an organization with that kind of past that would lead you to believe the use of it won't be ethical.
Collectors also come up a lot. You know it has been 2 years since they killed you. I understand that they weren't mentioned in the first game, but I think the intro mission was a really cool way to show what happened to you, and brought them into the picture in a very exciting way. Would it have been better if you had played that intro level at the end of ME1? It would totally ruin its effect because you KNOW Shepard has to live for the story to progress yet no explanation of how would be given. The forums would have been flooded for 2 years with theories on how Shepard comes back to life.
The point is the game was never intended as a 2 game series. They needed to leave each game feeling complete, so the 2 year wait in between won't seem like an eternity. When looking at a game/movie series with a huge budget, its not all the creative side of things it still has to make business sense. I plan on throwing down my cash on the next installment just like the last two, and have no regrets doing it. That is a lot more than can be said about quite a few games I feel I wasted my money on.