I went with Yes Man, then House, THEN Legion, and LASTLY NCR. It's really saying something that I would put them off till the very end. They're not that great of an ending. Meanwhile my favorite endings, and what I'd consider "the best" possible endings, are somewhere between Yes Man and House. They gave the best futures for New Vegas AND those communities shielded by its umbrella. House demanded more sacrifice for the future when he could not allow the BOS to live, but the Independent Vegas was not nearly as safe as House's proved to be. It's really up to the player to decide what ideal they value higher; humanity's future, or humanity's freedom. That's a tough call, and neither NCR nor Caesar have ANYTHING remotely close that they could offer.