I don't really see why destroying every reaper, and with them, possibly millions of years worth of knowledge is a good thing. But hey, they were the ones attacking us, It's not like we had a choice...except Commander Shepard did, and he wiped out the reapers, because they tried to wipe out everyone else. I'm not saying it's not fair, but it's kinda cruel and seem like a waste.
Also, this ending shows that you can do anything and there will be no serious consequences. Everyone will live (the important ones anyway, who care about the rest?). Every major problem will be solved somehow. Commander Shepard will happily sail the sea of stars "just like in the old days". Moral: using force is the best solution, even if you had several other choices. Of course, those were left out from this because everyone who played through mass effect as a paragon should probably feel that choosing destruction cannot be the "right" choice.
Forgiveness got Shepard the help of the Rachnii, helped the Quarians and the Geth understand each other. Throughout the whole game, the Commander showed everyone that undertanding and forgiveness, the ability to see that no matter how big you think the picture youu see is, there is always a bigger one, is the most important for a peaceful universe. If you played her or him as a paragon, then you choose these choices throughout the game. If, in the end, forgiveness and understanding, or at least the effort to do so is not an option, then what's the point?
While I won't argue with anyone who hated the star child (I didn't, but he's kinda wierd) and I will respect anyone's opinion for how the ending could have been better, but I don't really understand why destruction and full happy end is the only ending so many of us can imagine to be acceptable.