I don't want to spoil anything about Mass Effect 3 for you, so all you really need to know is this: Yes. Yes, you should get it. Yes, it lives up to the hype. Yes, it's the ending the series deserves. Yes, it's an incredible adventure that will terrify you, make you laugh, and more than likely move you to tears more than once. And yes, that character you care about comes back.
As the game begins, the Reapers have made Earth the first stop on their harvesting tour of the galaxy. Their arrival signals not just the end of the world, but the end of every world as they set out to destroy all organic life. Your experience with the Reapers makes you the best choice to fight them, and the Alliance is willing to let bygones be bygones - and give you back your ship - if you lead the charge against the Reaper armada. Your mission in Mass Effect 3 echoes that of Mass Effect 2: Then, you were gathering resources and personnel in hopes of increasing your chances of surviving a suicide mission. Now, you're doing much the same thing in the hopes of increasing your chances in a face-off against the Reapers ... which is also probably a suicide mission.
You don't have to have played through either of the first two Mass Effects in order to enjoy Mass Effect 3, as the game does a pretty good job on catching you up on the important people and events from its predecessors without dropping huge walls of text on your head. Saving the Earth is also a pretty easy concept to grasp, so even complete newcomers to the story should have no trouble embracing the adventure. Even though you can jump in just fine, there's no question that your experience will be greatly enriched if you played through the first two games. Mass Effect 3 does a masterful job of calling back to the first two games, their DLC, and even the Mass Effect novels, referencing practically every encounter you had or decision you made. The world of Mass Effect 3 feels lived in and worn out, and that effect just isn't quite the same if you don't understand the full weight of the experiences that have made these characters who they are. You can understand the basics about Maelon's genophage research with just a few lines of dialog, but his work takes on a whole new timbre when you've seen its effects first-hand.
One of Mass Effect's core strengths has been its story, which is particularly well crafted in Mass Effect 3, in part because it gets to tie up so many loose ends. Rather than leaving options open for a sequel, the game makes the most of the chance to take the sum of your decisions and show you the outcome. What did you do with the Rachni queen? What did you tell Conrad? Did you dance? It almost all comes back, one way or another, but never in a way that feels forced. Everything you experience in Mass Effect 3 feels like the natural, organic culmination of your actions - whether you can live with the repercussions or not.