I was originally thinking the Relays would all at the same time svck in every locked on Reaper in the universe. They would be forced to fire out of the mass relays and into some point in dark space beyond not only the galaxy but the universe. The Citadel would act like a gun. Then my friend pointed out something more ingenious point into the center of the universe launching the entirety of the Reaper fleet into the black hole/whatever is there. If that fails fire them into the dense cluster of the galactic core. It was made clear that the Reapers found a safe pocket within it, and volleying them into the core would result in their death. It even makes sense based on established lore of what and how the Mass Relays work. The good ending is Shepard surviving and the Reapers destroyed, heavy casualties though. The moderate ending see's Shepard sacrifice himself because the Cataclyst wasn't built properly. It unintentionally has to launch itself to the destination or something. The bad ending is the Catalyst wasn't built well enough and fails to function. Unless you've put in work to have another option at this point your only met with defeat. The Control option should remain, but take out the crack pot AI god somehow. You could explain it as the Illusive Man was well prepared and ready to take control of the Reapers at the moment of Shepard's arrival. Then a cinematic based on what ending you choose, and then finally some slides showing what the [censored] happened to everyone.

What should I choose for the best ending? Control the reapers, destroy the whatever they are, or synthesize?

I went with the synthesis ending, myself, and it seems to be intended to be the "good" ending, in that you need to have a relatively high Effective Military Strength to even have that as an option. But, I'd go with what feels right for your character. As others have said, it all turns out pretty much the same, regardless of what you choose.

Killing the Reapers, I think it's the one on the right.

But that also kills the Geth, and I would never kill the Geth. Ahhhhh so many decisions! What about controlling the reapers? Would that be the good or bad thing to do?

I don't know the specifics as I choose to destroy the Reapers but from what I gather it wasn't a completely evil choice.

I think Synthesis was intended to be the most "paragon" choice, as it's basically the "bring peace between organics and synthetics" option. I think it's more morally problematic than the game suggests, but I think it was intended to be the peace-maker option.

I went with Control, myself. It seems to be the only option that gives the galaxy any chance at getting back to normal.

That's what I ended up choosing.

It was an alright ending. Could have been better. Just a little disappointed that that was it and there wasn't more to it.

Ok so now that all the Mass Relays are blown to pieces does that mean the end of inter-system travel for all of eternity? And that whatever species where trapped in each system will inhabit that system now? So pretty much most of the Quarians and Turians are now residents of Sol? And There's going to be a hell of a lot of Krogan on Palaven as well. So what's going to happen with society and all?

I would think they would still be able to travel between star systems using FTL travel, as we only needed to use the Mass Relays in the game to travel between clusters. But the cinematic at the end of the credits seems to imply that interstellar travel is indeed ended. My guess is the future of the series will focus on rebuilding, perhaps with a more anarchic galaxy.