After play ME 1 & 2 the evolution to 3 is incredible.
The story line and how your decisions effect the story line is what makes this game better than all others. People try and compare this to other games but no other game fits. Yeah it's sort of like Gears of War & Final Fantasy, but at the same time it's not. It's a true original.
As far the ending goes, there's a lot of haters, but I thought it was very fitting and satisfying. Also note that there are different endings depending on how much you do.